Fastening tool

ABSTRACT

A fastening tool includes: a bit holding portion which detachably holds a driver bit and is configured to rotate in a circumferential direction of the driver bit and move in an axial direction of the driver bit; a first motor configured to rotate the bit holding portion; a second motor configured to move the bit holding portion along the axial direction; and a control unit configured to control a position of the bit holding portion along the axial direction by the number of rotations of the second motor. The control unit is configured to control a moving speed of a screw moved by rotation of the first motor or a rotation speed of the first motor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2021-149655 filed on Sep. 14, 2021,Japanese Patent Application No. 2021-149656 filed on Sep. 14, 2021,Japanese Patent Application No. 2021-149657 filed on Sep. 14, 2021,Japanese Patent Application No. 2022-067701 filed on Apr. 15, 2022, andJapanese Patent Application No. 2022-067704 filed on Apr. 15, 2022, thecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a fastening tool in which a driver bitis engaged with a screw, the screw is pressed against a fastening targetby the driver bit, and the driver bit is rotated to screw.

BACKGROUND ART

There is a tool called a portable striking machine which uses an airpressure of compressed air supplied from an air compressor or acombustion pressure of gas to sequentially strike connection stoppersloaded in a magazine from a tip end of a driver guide.

As a tool which rotates a bit to tighten a screw and moves the bit in adirection of tightening the screw, a pneumatic screw driving machine isproposed in the related art, in which the bit is rotated by an air motorand moved in a direction of tightening the screw by an air pressure (forexample, see Publication of Japanese Patent No. 5262461).

A screwdriver is proposed in which a spring is compressed by a drivingforce of a motor which rotates a screw, and the screw is driven bybiasing of the spring (for example, see Publication of Japanese PatentNo. 6197547).

In a tool having a configuration in which a bit is moved in a directionof tightening a screw, the faster a forward speed of the bit than aforward speed of the screw determined by a rotation speed of the screw,the greater a so-called reaction that separates a tool body from afastening target. When the reaction becomes large, the tool body mayfloat up from the fastening target, resisting a force with which anoperator presses the tool body against the fastening target.

However, if the tool body floats up from the fastening target by thereaction, an operation may be completed in a state where the screwcannot be completely tightened.

Therefore, in order to improve quality of screw tightening, it isnecessary to prevent the reaction, that is, to operate the bit (move thebit forward) at an appropriate speed in accordance with the rotationspeed of the screw.

However, in a fastening tool in the related art, there is no idea ofcontrolling the forward speed of the bit in accordance with the rotationspeed. In both of the screw driving machine which uses the air pressureand the screwdriver which drives the screw by biasing of the spring, itis difficult to control a moving speed of a driver bit by an operationof moving the driver bit in a direction of tightening the screw.

The present disclosure is made to solve such a problem, and an object ofthe present disclosure is to provide a fastening tool capable ofcontrolling a moving speed of a driver bit by an operation of moving thedriver bit in a direction of tightening a screw.

SUMMARY

An aspect of the present disclosure relates to a fastening toolincluding: a bit holding portion which detachably holds a driver bit andis configured to rotate in a circumferential direction of the driver bitand move in an axial direction of the driver bit; a first motorconfigured to rotate the bit holding portion; a second motor configuredto move the bit holding portion along the axial direction; and a controlunit configured to control a position of the bit holding portion alongthe axial direction by the number of rotations of the second motor. Thecontrol unit is configured to control a moving speed of a screw moved byrotation of the first motor or a rotation speed of the first motor.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a side cross-sectional view showing an example of an internalstructure of a fastening tool according to the present embodiment.

FIG. 1B is a top cross-sectional view showing an example of the internalstructure of the fastening tool according to the present embodiment.

FIG. 1C is a front cross-sectional view showing an example of theinternal structure of the fastening tool according to the presentembodiment.

FIG. 2A is an exploded perspective view showing an example of theinternal structure of the fastening tool according to the presentembodiment.

FIG. 2B is an external perspective view showing an example of thefastening tool according to the present embodiment.

FIG. 3A is a perspective view showing an example of configurations ofmain parts of the fastening tool according to the present embodiment.

FIG. 3B is a perspective view showing an example of configurations ofmain parts of the fastening tool according to the present embodiment.

FIG. 4A is a cross-sectional perspective view showing an example ofconfigurations of main parts of the fastening tool according to thepresent embodiment.

FIG. 4B is a cross-sectional perspective view showing an example ofconfigurations of main parts of the fastening tool according to thepresent embodiment.

FIG. 4C is a cross-sectional perspective view showing an example ofconfigurations of main parts of the fastening tool according to thepresent embodiment.

FIG. 5 is a top cross-sectional view showing an example ofconfigurations of main parts of the fastening tool according to thepresent embodiment.

FIG. 6A is a top cross-sectional view showing an example of the internalstructure of the fastening tool according to the present embodiment.

FIG. 6B is a top cross-sectional view showing an example of the internalstructure of the fastening tool according to the present embodiment.

FIG. 7A is a cross-sectional view showing an example of an attachmentand detachment holding mechanism.

FIG. 7B is a cross-sectional view showing an example of the attachmentand detachment holding mechanism.

FIG. 8A is a perspective view showing an example of the attachment anddetachment holding mechanism.

FIG. 8B is a perspective view showing an example of the attachment anddetachment holding mechanism.

FIG. 9 is a perspective view showing an example of a screw feedingportion and a nose portion according to the present embodiment.

FIG. 10A is a perspective view showing an example of the fastening toolaccording to the present embodiment as viewed from a rear side.

FIG. 10B is a perspective view showing an example of the fastening toolaccording to the present embodiment as viewed from the rear side.

FIG. 10C is a perspective view showing an example of the fastening toolaccording to the present embodiment as viewed from the rear side.

FIG. 11 is a perspective view showing an example of a setting portion.

FIG. 12 is a block diagram showing an example of the fastening toolaccording to the present embodiment.

FIG. 13A is a side cross-sectional view showing an example of anoperation of the fastening tool according to the present embodiment.

FIG. 13B is a top cross-sectional view showing an example of theoperation of the fastening tool according to the present embodiment.

FIG. 14 is a flowchart showing an example of the operation of thefastening tool according to the present embodiment.

FIG. 15A is a cross-sectional view showing a fastening state of a screw.

FIG. 15B is a cross-sectional view showing a fastening state of thescrew.

FIG. 15C is a cross-sectional view showing a fastening state of thescrew.

FIG. 16A is a diagram showing an example of an operation of setting astandby position of a holding member and a moving member in a firstinitialization operation.

FIG. 16B is a diagram showing an example of the operation of setting thestandby position of the holding member and the moving member in thefirst initialization operation.

FIG. 16C is a diagram showing an example of the operation of setting thestandby position of the holding member and the moving member in thefirst initialization operation.

FIG. 16D is a diagram showing an example of the operation of setting thestandby position of the holding member and the moving member in thefirst initialization operation.

FIG. 17A is a diagram showing an example of an operation of moving theholding member and the moving member to the standby position in a secondinitialization operation.

FIG. 17B is a diagram showing an example of the operation of moving theholding member and the moving member to the standby position in thesecond initialization operation.

FIG. 17C is a diagram showing an example of the operation of moving theholding member and the moving member to the standby position in thesecond initialization operation.

FIG. 18 is a flowchart showing an example of an operation of selectingthe first initialization operation and the second initializationoperation.

FIG. 19 is a flowchart showing a modification of the operation of thefastening tool according to the present embodiment.

FIG. 20 is a graph showing a relationship between output of a contactswitch portion and control over a bit rotation motor and a bit movementmotor.

FIG. 21 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment.

FIG. 22A is a graph showing a relationship between a load and controlover the bit rotation motor.

FIG. 22B is a graph showing a relationship between a load and controlover the bit rotation motor.

FIG. 23 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment.

FIG. 24A is a graph showing a relationship between rotation speeds ofthe bit rotation motor and the bit movement motor under feedbackcontrol.

FIG. 24B is a graph showing a relationship between a moving speed of thescrew by rotation of the bit rotation motor and a moving speed of adriver bit by the bit movement motor under the feedback control.

FIG. 25 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment.

FIG. 26A is a graph showing a relationship between a load and controlover the bit movement motor.

FIG. 26B is a graph showing a relationship between a load and controlover the bit movement motor.

FIG. 27 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment.

FIG. 28 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment.

FIG. 29 is a block diagram showing another modification of the operationof the fastening tool according to the present embodiment.

FIG. 30 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment.

FIG. 31 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment.

FIG. 32 is a graph showing a relationship between a load and controlover the bit movement motor at the time of screw tightening.

FIG. 33 is a view showing an engagement state between the driver bit anda recess of the screw at the time of the screw tightening.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of a fastening tool according to the presentdisclosure will be described with reference to the drawings.

Configuration Example of Fastening Tool According to Present Embodiment

FIG. 1A is a side cross-sectional view showing an example of an internalstructure of the fastening tool according to the present embodiment.

FIG. 1B is a top cross-sectional view showing an example of the internalstructure of the fastening tool according to the present embodiment.

FIG. 1C is a front cross-sectional view showing an example of theinternal structure of the fastening tool according to the presentembodiment.

FIG. 2A is an exploded perspective view showing an example of theinternal structure of the fastening tool according to the presentembodiment.

FIG. 2B is an external perspective view showing an example of thefastening tool according to the present embodiment.

The fastening tool 1 according to the present embodiment includes a bitholding portion 3 that holds a driver bit 2 so as to be rotatable andmovable in an axial direction, a first drive unit 4 that rotates thedriver bit 2 held by the bit holding portion 3, and a second drive unit5 that moves the driver bit 2 held by the bit holding portion 3 in theaxial direction.

The fastening tool 1 includes a screw accommodating portion 6 in which ascrew 200 is accommodated, a screw feeding portion 7 that feeds thescrew accommodated in the screw accommodating portion 6, and a noseportion 8 that is pressed against a fastening target to which the screw200 is fastened and into which the screw is injected.

Further, the fastening tool 1 includes a tool body 10 and a handle 11.The fastening tool 1 includes a battery attachment portion 13 to which abattery 12 is detachably attached at an end portion of the handle 11.

In the fastening tool 1, the tool body 10 extends in one direction alongthe axial direction of the driver bit 2 indicated by arrows A1 and A2,and the handle 11 extends in another direction intersecting an extendingdirection of the tool body 10. In the fastening tool 1, a direction inwhich the tool body 10 extends, that is, the axial direction of thedriver bit 2 indicated by the arrows A1 and A2 is a front-reardirection. In the fastening tool 1, a direction in which the handle 11extends is an upper-lower direction. Further, in the fastening tool 1, adirection orthogonal to the extending direction of the tool body 10 andan extending direction of the handle 11 is a left-right direction.

The first drive unit 4 is provided on a rear side, which is one side ofthe tool body 10, with the handle 11 interposed therebetween.

The second drive unit 5 is provided on a front side, which is the otherside of the tool body 10, with the handle 11 interposed therebetween.

In the screw accommodating portion 6, a plurality of screws 200 areconnected by a connecting band, and a connecting screw wound in a spiralshape is accommodated.

FIGS. 3A and 3B are perspective views showing an example ofconfigurations of main parts of the fastening tool according to thepresent embodiment. FIGS. 4A to 4C are cross-sectional perspective viewsshowing an example of configurations of main parts of the fastening toolaccording to the present embodiment. FIG. 5 is a top cross-sectionalview showing an example of configurations of main parts of the fasteningtool according to the present embodiment, and shows details of the bitholding portion 3 and the first drive unit 4. Next, the bit holdingportion 3 and the first drive unit 4 will be described with reference tothe drawings.

The bit holding portion 3 is an example of a tip end tool holdingportion, and includes a holding member 30 that detachably holds thedriver bit 2, which is an example of a tip end tool, a rotation guidemember 31 that supports the holding member 30 so as to be movable in thefront-rear direction indicated by the arrows A1 and A2 along the axialdirection of the driver bit 2 and rotates together with the holdingmember 30, a moving member 32 that moves the holding member 30 in thefront-rear direction along the rotation guide member 31, and a biasingmember 33 that biases the moving member 32 in a rear direction indicatedby the arrow A2.

The holding member 30 has an outer diameter slightly smaller than aninner diameter of the rotation guide member 31, and is formed of, forexample, a columnar member inserted inside the rotation guide member 31.In the holding member 30, an opening 30 a having a shape matching across-sectional shape of the driver bit 2 is provided at an end portionon a front side along the axial direction of the driver bit 2. Theholding member 30 includes, in the opening 30 a, an attachment anddetachment holding mechanism 30 c that detachably holds the driver bit2. In the holding member 30, the opening 30 a is exposed to an inside ofthe rotation guide member 31, and the driver bit 2 is detachablyinserted into the opening 30 a.

The rotation guide member 31 extends along the extending direction ofthe tool body 10, that is, along the front-rear direction indicated bythe arrows A1 and A2 along the axial direction of the driver bit 2. Therotation guide member 31 has a cylindrical shape into which the holdingmember 30 enters, and an end portion on a front side of the rotationguide member 31 is rotatably supported by a metal front frame 10 bprovided on a front side of a resin case 10 a forming an exterior of thetool body 10 via a bearing 34 a that is an example of a bearing. An endportion on a rear side of the rotation guide member 31 is connected tothe first drive unit 4.

In the rotation guide member 31, groove portions 31 a extending in thefront-rear direction indicated by the arrows A1 and A2 along the axialdirection of the driver bit 2 are formed at two positions of sideportions facing each other in a radial direction. The rotation guidemember 31 penetrates the holding member 30 in the radial direction, anda connecting member 30 b protruding from both sides of the holdingmember 30 enters the groove portions 31 a, so that the rotation guidemember 31 is connected to the holding member 30 via the connectingmember 30 b.

The holding member 30 is provided with a hole portion penetrating in adirection perpendicular to a rotation direction of the driver bit 2, andthe connecting member 30 b is inserted into the hole portion and fixedby a pin 30 f. The connecting member 30 b is formed of a tubular memberhaving an oval cross-sectional shape.

The connecting member 30 b is oriented with a longitudinal direction ofthe oval shape along an extending direction of the groove portion 31 aparallel to the axial direction of the driver bit 2 indicated by thearrows A1 and A2, a lateral direction of the oval shape orthogonal tothe extending direction of the groove portion 31 a indicated by arrowsB1 and B2, that is, along a rotation direction of the rotation guidemember 31. The connecting member 30 b is configured such that a width ofthe lateral direction of the oval shape, that is, a width of therotation guide member 31 along the rotation direction is slightlysmaller than a width of the groove portion 31 a along the samedirection.

Accordingly, the connecting member 30 b inserted into the groove portion31 a is supported by the groove portion 31 a so as to be movable alongan axial direction of the rotation guide member 31. Movement of theconnecting member 30 b along the rotation direction with respect to therotation guide member 31 is restricted between one side surface and theother side surface of the groove portion 31 a along the extendingdirection of the groove portion 31 a. Therefore, by an operation ofrotating the rotation guide member 31, the connecting member 30 b ispressed by one side surface or the other side surface of the grooveportion 31 a according to the rotation direction of the rotation guidemember 31, and receives a force in a circumferential direction which isthe rotation direction from the rotation guide member 31.

Therefore, when the rotation guide member 31 rotates, the connectingmember 30 b is pressed by the groove portion 31 a of the rotation guidemember 31, so that the holding member 30 rotates together with therotation guide member 31. The connecting member 30 b is guided by thegroove portion 31 a of the rotation guide member 31, and the holdingmember 30 moves in the front-rear direction along the axial direction ofthe driver bit 2.

The moving member 32 is an example of a transmission member, andincludes a first moving member 32 a which rotates together with theholding member 30 and moves the holding member 30 in the front-reardirection along the rotation guide member 31, a second moving member 32c which is supported by the first moving member 32 a via a bearing 32 band presses the first moving member 32 a via the bearing 32 b, and abuffer member 32 d which is attached to a rear side of the second movingmember 32 c.

The first moving member 32 a has an inner diameter slightly larger thanan outer diameter of the rotation guide member 31, and is formed of, forexample, a cylindrical member inserted outside the rotation guide member31. The first moving member 32 a is connected to the holding member 30via the connecting member 30 b protruding from the groove portion 31 aof the rotation guide member 31, so that the first moving member 32 a issupported so as to be movable along the axial direction of the rotationguide member 31.

The bearing 32 b is an example of the bearing and is inserted between anouter circumference of the first moving member 32 a and an innercircumference of the second moving member 32 c. The first moving member32 a forms a bearing inner ring holding member which holds an inner ringof the bearing 32 b, and the second moving member 32 c forms a bearingouter ring holding member which holds an outer ring of the bearing 32 b.In the bearing 32 b, the inner ring is supported on the outercircumference of the first moving member 32 a so as not to be movable inthe rotation direction and the axial direction, and the outer ring issupported on the inner circumference of the second moving member 32 c soas not to be movable in the rotation direction and the axial direction.

Accordingly, the second moving member 32 c is connected to the firstmoving member 32 a via the bearing 32 b in a state in which movement ofthe second moving member 32 c in the front-rear direction along theaxial direction is restricted. The second moving member 32 c rotatablysupports the first moving member 32 a via the bearing 32 b.

Therefore, the first moving member 32 a is pressed by the second movingmember 32 c via the bearing 32 b by a movement operation of the secondmoving member 32 c in the front-rear direction along the axialdirection, and moves in the front-rear direction along the axialdirection together with the second moving member 32 c. The first movingmember 32 a is rotatable with respect to the second moving member 32 cthat is not rotatable with respect to the rotation guide member 31.

The biasing member 33 is formed of a coil spring in the present example,is outside the rotation guide member 31, and is inserted between thefront frame 10 b provided on the front side of the case 10 a of the toolbody 10 and the second moving member 32 c of the moving member 32, andabuts against a spring seat 32f that contacts an end surface of theouter ring of the bearing 32 b. The biasing member 33 is compressed bymovement of the moving member 32 in a forward direction indicated by thearrow A1, and applies a force for pressing the moving member 32 in arearward direction indicated by the arrow A2 to the moving member 32.

The first drive unit 4 includes a bit rotation motor 40 which is drivenby electricity supplied from the battery 12, and a speed reducer 41. Thebit rotation motor 40 is an example of a motor or a first motor, and ashaft 40 a of the bit rotation motor 40 is connected to the speedreducer 41, and a shaft 41 a of the speed reducer 41 is connected to therotation guide member 31. In the first drive unit 4, the speed reducer41 uses planetary gears, and the bit rotation motor 40 is disposedcoaxially with the rotation guide member 31, the holding member 30, andthe driver bit 2 held by the holding member 30.

In the first drive unit 4, the bit rotation motor 40 and the speedreducer 41 are attached to a metal rear frame 10 c provided on a rearside of the case 10 a of the tool body 10, and the shaft 41 a of thespeed reducer 41 is supported by the rear frame 10 c via a bearing 42.The end portion on the rear side of the rotation guide member 31 isconnected to the shaft 41 a of the speed reducer 41, and the shaft 41 ais supported by the rear frame 10 c via the bearing 42, so that therotation guide member 31 is rotatably supported via the bearing 42,which is an example of the bearing.

The bit holding portion 3 and the first drive unit 4 are integrallyassembled by connecting the front frame 10 b and the rear frame 10 c bya coupling member 10 d extending in the front-rear direction, and thefront frame 10 b is fixed to the case 10 a of the tool body 10 by ascrew 10 e.

In the bit holding portion 3, the end portion on the front side of therotation guide member 31 is supported by the front frame 10 b fixed tothe front side of the case 10 a of the tool body 10 via the bearing 34a, and the end portion on the rear side of the rotation guide member 31is supported by the rear frame 10 c fixed to the rear side of the case10 a via the shaft 41 a of the speed reducer 41 and the bearing 42.Therefore, in the bit holding portion 3, the rotation guide member 31 isrotatably supported by the tool body 10.

Accordingly, the first drive unit 4 rotates the rotation guide member 31by the bit rotation motor 40. When the rotation guide member 31 rotates,the connecting member 30 b is pressed by the groove portion 31 a of therotation guide member 31, so that the holding member 30 holding thedriver bit 2 rotates together with the rotation guide member 31.

In the bit holding portion 3, the second moving member 32 c is providedwith a guide member 32 g. The coupling member 10 d is provided with apair of guide wall portions 10 g at an interval slightly larger than adiameter of the guide member 32 g, and the guide member 32 g entersbetween the pair of guide wall portions 10 g, the pair of guide wallportions 10 g face a circumferential surface of the guide member 32 g.

Accordingly, the guide member 32 g is guided by the coupling member 10d, so that the second moving member 32 c is movable in the front-reardirection indicated by the arrows A1 and A2 along the axial direction ofthe driver bit 2, and rotation of the second moving member 32 cfollowing the rotation guide member 31 is restricted.

FIGS. 6A and 6B are top cross-sectional views showing an example of aninternal structure of the fastening tool according to the presentembodiment, and show details of the second drive unit 5. Next, thesecond drive unit 5 will be described with reference to the drawings.

The second drive unit 5 includes a bit movement motor 50 which is drivenby electricity supplied from the battery 12, and a speed reducer 51. Thebit movement motor 50 is an example of a motor or a second motor, and ashaft 50 a of the bit movement motor 50 is connected to the speedreducer 51, and a shaft 51 a of the speed reducer 51 is connected to apulley 52 which is an example of the transmission member. In the seconddrive unit 5, the pulley 52 is supported by the tool body 10 via abearing 53. In the second drive unit 5, the shaft 50 a of the bitmovement motor 50 is disposed along the extending direction of thehandle 11.

In the second drive unit 5, one end of a linear wire 54, which is anexample of the transmission member, is connected to the pulley 52, andthe wire 54 is wound around the pulley 52 by rotation of the pulley 52.The other end of the wire 54 is connected to a wire connecting portion32 h provided in the second moving member 32 c of the moving member 32.

Accordingly, the second drive unit 5 rotates the pulley 52 by the bitmovement motor 50 to wind the wire 54, thereby moving the second movingmember 32 c in the forward direction indicated by the arrow A1. In thebit holding portion 3, when the second moving member 32 c moves in theforward direction, the first moving member 32 a is pressed via thebearing 32 b, and the first moving member 32 a moves in the forwarddirection along the axial direction together with the second movingmember 32 c. When the first moving member 32 a moves in the forwarddirection, the holding member 30 connected to the first moving member 32a via the connecting member 30 b moves in the forward direction, and thedriver bit 2 held by the holding member 30 moves in the forwarddirection indicated by the arrow A1.

The second drive unit 5 is offset to one side with respect to asubstantially center of the fastening tool 1 in the left-right directionsuch that a tangential direction of a portion of the pulley 52 aroundwhich the wire 54 is wound is along an extending direction of therotation guide member 31. That is, a center of the pulley 52, in thepresent example, the shaft 50 a of the bit movement motor 50 is offsetto one side with respect to the rotation guide member 31, and a portion52 a of the pulley 52 around which the wire 54 is wound overlaps therotation guide member 31 when viewed from an axial direction of thepulley 52.

The pulley 52 and the like are disposed such that the wire 54 betweenthe pulley 52 and the second moving member 32 c is parallel to the axialdirection of the rotation guide member 31 in a radial direction of thepulley 52 as shown in FIGS. 6A and 6B, and is parallel to the axialdirection of the rotation guide member 31 also in an axial direction ofthe bit movement motor 50 orthogonal to the radial direction of thepulley 52 as shown in FIG. 1A.

Further, when the wire 54 is wound on the pulley 52 in an overlappingmanner, a distance from a center of the pulley 52 to the wire 54 changesaccording to the number of turns, so that a movement amount of thedriver bit 2 when the pulley 52 makes one rotation changes. An angleformed by a direction in which the wire 54 extends between the pulley 52and the second moving member 32 c and a moving direction of the driverbit 2 along the axial direction of the rotation guide member 31 changes.

Therefore, a diameter and the like of the pulley 52 are set so that arotation amount a of the pulley 52 necessary for moving the driver bit 2by a predetermined amount is less than 360°.

Accordingly, when the pulley 52 winds the wire 54 in order to move thedriver bit 2 by a predetermined amount, as shown in FIG. 6B, the wire 54is not wound around the pulley 52 in an overlapping manner, and themovement amount of the driver bit 2 is prevented from becominginaccurate. A change in parallelism between the direction in which thewire 54 extends between the pulley 52 and the second moving member 32 cand the moving direction of the driver bit 2 along the axial directionof the rotation guide member 31 is prevented.

Therefore, a relationship between the number of rotations of the bitmovement motor 50 and a movement amount of the holding member 30 becomesa one-to-one relationship in an entire movable range of the holdingmember 30, and the movement amount of the holding member 30 along theaxial direction of the rotation guide member 31 can be controlled bycontrolling the number of rotations of the bit movement motor 50. Thatis, the movement amount of the driver bit 2 attached to the holdingmember 30 can be controlled by controlling the number of rotations ofthe bit movement motor 50.

Regardless of a winding amount of the wire 54, a tension applied to thewire 54 is always parallel to the moving direction of the driver bit 2along the axial direction of the rotation guide member 31, and it ispossible to move the driver bit 2 and prevent a decrease of transmissionefficiency of a force for pressing the screw 200 via the driver bit 2.

Accordingly, the wire 54 between the pulley 52 and the second movingmember 32 c extends linearly along a moving direction of the movingmember 32, and an increase in a load when the wire 54 is wound by thepulley 52 and an increase in a load when the wire 54 is pulled out fromthe pulley 52 are prevented.

Since the wire 54 is flexible enough to be wound around the pulley 52,the wire 54 cannot press the second moving member 32 c to move themoving member 32 rearward. Therefore, the biasing member 33 is providedwhich is compressed by the movement of the moving member 32 in theforward direction indicated by the arrow A1, and that applies the forcefor pressing the moving member 32 in the rearward direction indicated bythe arrow A2 to the moving member 32. Accordingly, the wire 54 is woundby the pulley 52 to move the driver bit 2 forward, so that the driverbit 2 after moving forward can be moved rearward.

By engagement between the connecting member 30 b provided in the holdingmember 30 and the groove portion 31 a provided in the rotation guidemember 31, the holding member 30 holding the driver bit 2 is supportedso as to be movable in the front-rear direction with respect to therotation guide member 31 and rotates together with the rotation guidemember 31.

Therefore, in a configuration in which the bit rotation motor 40 isdisposed coaxially with the rotation guide member 31 and the holdingmember 30 and the driver bit 2 held by the holding member 30, it ispossible to implement a configuration in which the driver bit 2 isrotated and the driver bit 2 is moved in the front-rear directionwithout moving the bit rotation motor 40 in the front-rear direction.

In the configuration in which the bit rotation motor 40 is disposedcoaxially with the driver bit 2, a configuration is considered in whicha rotation operation of the bit rotation motor 40 is converted intomovement of the driver bit 2 in the front-rear direction by using a feedscrew.

However, in the configuration using the feed screw, a forward movementamount of the driver bit 2 per rotation of the motor cannot beincreased, so that it is difficult to increase a moving speed of thedriver bit 2 even when a rotation speed of the motor is increased.

In the fastening tool 1, in order to shorten a time required to pressthe screw 200 against the fastening target by the driver bit 2, it isnecessary to increase the moving speed of the driver bit 2. However, inthe configuration using the feed screw, it is difficult to shorten thetime until the screw 200 is pressed against the fastening target by thedriver bit 2.

On the other hand, in the configuration in which the holding member 30holding the driver bit 2 is supported so as to be movable in thefront-rear direction with respect to the rotation guide member 31, thepulley 52 is rotated by the second drive unit 5 to wind up the wire 54,and the holding member 30 is moved in the forward direction, the movingspeed of the driver bit 2 can be increased according to a rotation speedof the bit movement motor 50. Therefore, it is possible to shorten thetime until the screw 200 is pressed against the fastening target by thedriver bit 2.

FIGS. 7A and 7B are cross-sectional views showing examples of theattachment and detachment holding mechanism. FIGS. 8A and 8B areperspective views showing examples of the attachment and detachmentholding mechanism, and shows details of the attachment and detachmentholding mechanism 30 c. Next, the attachment and detachment holdingmechanism 30 c will be described with reference to the drawings.

The attachment and detachment holding mechanism 30 c includes a ball 30d exposed in the opening 30 a and a spring 30 e that biases the ball 30d in a direction of exposing the ball 30 d in the opening 30 a. Thespring 30 e is formed of an annular leaf spring and is fitted to anouter circumference of the holding member 30.

When an insertion portion 20 of the driver bit 2 is inserted into theopening 30 a of the holding member 30, the attachment and detachmentholding mechanism 30 c retracts in an outer circumferential direction ofthe holding member 30 while the ball 30 d pressed by the insertionportion 20 deforms the spring 30 e in a direction of increasing adiameter of the annular spring 30 e.

When the insertion portion 20 of the driver bit 2 is inserted into theopening 30 a of the holding member 30 to a position where a grooveportion 20 a formed on an outer circumference of the insertion portion20 faces the ball 30 d, the ball 30 d biased by the spring 30 e isfitted into the groove portion 20 a. Accordingly, the driver bit 2 isprevented from being inadvertently detached from the holding member 30.

When a force equal to or greater than a predetermined force is appliedin a direction of pulling the driver bit 2 out from the holding member30, the ball 30 d retracts while deforming the spring 30 e in thedirection of increasing the diameter of the annular spring 30 e, so thatthe driver bit 2 can be pulled out from the holding member 30.

In operations of inserting and removing the insertion portion 20 of thedriver bit 2 into and from the opening 30 a of the holding member 30,the ball 30 d retracts in the outer circumferential direction of theholding member 30. Therefore, a space for the ball 30 d retracting isrequired in the outer circumference of the holding member 30. On theother hand, since the holding member 30 is inserted into the tubularrotation guide member 31, a space for the ball 30 d retracting cannot besecured between the outer circumference of the holding member 30 and aninner circumference of the rotation guide member 31.

When a diameter difference between the holding member 30 and therotation guide member 31 is set in order to secure the space for theball 30 d retracting between the outer circumference of the holdingmember 30 and the inner circumference of the rotation guide member 31,the outer diameter of the holding member 30 cannot be reduced because adimension of the driver bit 2 in the radial direction is determined, sothat it is necessary to increase the outer diameter of the rotationguide member 31. Therefore, a size of the device is increased.

On the other hand, the rotation guide member 31 is provided with thegroove portion 31 a that guides the connecting member 30 b. The grooveportion 31 a penetrates from an inner circumferential side to an outercircumferential side of the rotation guide member 31 on the front andrear sides, and extends in the axial direction of the rotation guidemember 31.

Therefore, in the attachment and detachment holding mechanism 30 c, theball 30 d is provided in accordance with a position in the grooveportion 31 a of the rotation guide member 31. That is, in the holdingmember 30, the connecting member 30 b and the ball 30 d of theattachment and detachment holding mechanism 30 c are provided coaxiallyalong the axial direction of the rotation guide member 31. Accordingly,in the attachment and detachment holding mechanism 30 c, the ball 30 dis exposed to the groove portion 31 a of the rotation guide member 31 inboth operations of rotating the rotation guide member 31 and the holdingmember 30 and an operation of moving the holding member 30 in the axialdirection with respect to the rotation guide member 31.

Therefore, when the insertion portion 20 of the driver bit 2 is insertedinto or removed from the opening 30 a of the holding member 30, the ball30 d retracted in the outer circumferential direction of the holdingmember 30 enters the groove portion 31 a of the rotation guide member31.

Therefore, in the configuration in which the holding member 30 isinserted into the tubular rotation guide member 31, it is possible tosecure the space for the ball 30 d of the attachment and detachmentholding mechanism 30 c retracting. Since the groove portion 31 a intowhich the connecting member 30 b enters is also used as the space forthe ball 30 d retracting, an area of an opening provided in the rotationguide member 31 is reduced, and strength can be secured.

Further, the diameter difference between the holding member 30 and therotation guide member 31 is increased, so that it is not necessary tosecure the space for the ball 30 d retracting between the outercircumference of the holding member 30 and the inner circumference ofthe rotation guide member 31, and it is possible to prevent an increasein the size of the device.

FIG. 9 is a perspective view showing an example of a screw feedingportion and a nose portion according to the present embodiment, andshows details of the screw feeding portion 7 and the nose portion 8.Next, the screw feeding portion 7 and the nose portion 8 will bedescribed with reference to the drawings.

The screw feeding portion 7 includes a screw feeding motor 70, piniongears 71 attached to a shaft of the screw feeding motor 70 via a speedreducer, rack gears 72 meshing with the pinion gears 71, and anengagement portion 73 connected to the rack gears 72 and engaged with aconnecting screw fed from the screw accommodating portion 6.

In the screw feeding portion 7, the rack gears 72 are supported so as tobe movable in the upper-lower direction along a feeding direction of theconnecting screw. In the screw feeding portion 7, the screw feedingmotor 70 rotates forward and reversely, so that the engagement portion73 engaged with the connecting screw moves in the upper-lower direction,and the connecting screw is fed.

The nose portion 8 includes an injection passage 80 to which the screw200 is supplied by the screw feeding portion 7 and through which thedriver bit 2 passes, a contact member 81 that has an injection port 81 acommunicating with the injection passage 80 and contacts the fasteningtarget, a contact arm 82 that moves in the front-rear direction inconjunction with the contact member 81, and an adjustment portion 83that restricts a movement amount of the contact arm 82. The nose portion8 includes a cover member 88 that openably and closably covers a paththrough which the screw 200 passes from the screw accommodating portion6 to the injection passage 80.

The fastening tool 1 includes the nose portion 8 with each componentforming the injection passage 80, the contact member 81 and the contactarm 82 assembled, and the nose portion 8 is fixed to the front frame 10b and a nose body portion 10 f forming the tool body 10. The fasteningtool 1 includes a contact switch portion 84 that is operated by beingpressed by the contact arm 82.

In the nose portion 8, the contact member 81 is supported so as to bemovable in the front-rear direction indicated by the arrows A1 and A2,and the contact arm 82 moves in the front-rear direction in conjunctionwith the contact member 81. In the nose portion 8, the contact member 81is biased in the forward direction by a biasing member (not shown), andthe contact member 81 that is pressed against the fastening target andmoves rearward is biased by the biasing member and moves in the forwarddirection.

In the nose portion 8, the contact member 81 is pressed against thefastening target, the contact arm 82 moves rearward, and the movementamount of the contact arm 82 until the contact switch portion 84 isoperated is adjusted by the adjustment portion 83. The contact switchportion 84 is pressed by the contact arm 82 to switch presence orabsence of an operation. In the present example, a state in which thecontact switch portion 84 is not operated without being pressed by thecontact arm 82 is set to OFF of the contact switch portion 84, and astate in which the contact switch portion 84 is operated by beingpressed by the contact arm 82 is set to ON of the contact switch portion84.

Next, a configuration related to control over the fastening tool 1 andan operation of the fastening tool 1 will be described with reference tothe drawings. The fastening tool 1 includes a trigger 9 that receives anoperation and a trigger switch portion 90 that is operated by theoperation of the trigger 9. The trigger 9 is provided on the front sideof the handle 11, and is configured to be operable by a finger of a handgripping the handle 11. The trigger switch portion 90 is operated bybeing pressed by the trigger 9.

The trigger switch portion 90 is pressed by the trigger 9 to switchpresence or absence of an operation. In the present example, a state inwhich the trigger switch 90 is not operated without operating thetrigger 9 and without being pressed by the trigger 9 is set to OFF ofthe trigger switch 90, and a state in which the trigger switch 90 isoperated by operating the trigger 9 and being pressed by the trigger 9is set to ON of the trigger switch 90.

The fastening tool 1 includes a control unit 100 that controls the firstdrive unit 4, the second drive unit 5, and the screw feeding portion 7based on output of the trigger switch portion 90 operated by anoperation of the trigger 9 and the contact switch portion 84 operated bybeing pressed by the contact arm 82.

The control unit 100 is formed of a substrate on which variouselectronic components are mounted, and is provided in a substrateaccommodating portion 111 provided on a rear surface side of the screwaccommodating portion 6 between the screw accommodating portion 6 andthe handle 11.

In an electric power tool used by holding a handle with a hand, anaccommodating portion in which consumables such as screws areaccommodated is provided in front of the handle. In order to allow thehandle to be gripped by the hand, a space for fingers of the hand toenter is required between the handle and the accommodating portion.

Therefore, the fastening tool 1 includes the substrate accommodatingportion 111 on the rear surface side of the screw accommodating portion6 by using the space between the screw accommodating portion 6 and thehandle 11.

In an electric power tool used by holding a handle with a hand, aconfiguration is proposed in which a battery is attached to a lowerportion of the handle and a substrate is provided between the handle andthe battery. With such a configuration, a dimension in an upper-lowerdirection of the electric power tool along an extending direction of thehandle increases.

On the other hand, by providing the substrate accommodating portion 111on the rear surface side of the screw accommodating portion 6, adimension of the fastening tool 1 in the upper-lower direction along theextending direction of the handle 11 is prevented from increasing. Sincethe connecting screw wound in a spiral shape is accommodated in thescrew accommodating portion 6, a surface of the screw accommodatingportion 6 facing the handle 11 has a substantially circular shape.Accordingly, it is possible to secure a volume of the substrateaccommodating portion 111 while preventing an increase in the size ofthe fastening tool 1.

FIGS. 10A to 10C are perspective views showing examples of the fasteningtool according to the present embodiment as viewed from a rear side.FIG. 11 is a perspective view showing an example of a setting portionand shows details of a setting portion 110. Next, the setting portion110 will be described with reference to the drawings.

The fastening tool 1 includes the second drive unit 5 that moves thedriver bit 2 in the front-rear direction along the axial direction, inwhich the second drive unit 5 is driven by the bit movement motor 50,and the moving member 32 connected to the pulley 52, which is driven androtated by the bit movement motor 50, by the wire 54 and the holdingmember 30 connected to the moving member 32 move in the forwarddirection along the axial direction of the driver bit 2 along therotation guide member 31.

Accordingly, the movement amount (forward movement amount) of the driverbit 2 can be controlled by controlling the number of rotations of thebit movement motor 50. That is, by rotating the bit movement motor 50 inconjunction with rotation of the bit rotation motor 40 that rotates thedriver bit 2 in a direction of fastening the screw 200, it is possibleto control the forward movement amount of the driver bit 2 that movesforward following the screw 200 with fastening of the screw 200 by thenumber of rotations of the bit movement motor 50, and to control a stopposition of the driver bit 2 along the axial direction.

Therefore, the fastening tool 1 includes the setting portion 110 forsetting the forward movement amount of the driver bit 2. The settingportion 110 is an example of a setting unit, and is configured such thata desired set value can be selected from a plurality of setting values,or a desired set value can be selected steplessly.

In the present example, the setting portion 110 has a configuration inwhich a setting value is selected by an operation portion 110 a having abutton. An operation portion 110 a may have a configuration in which asetting value is selected by a rotary dial. The setting portion 110 maybe configured to display a selected setting value by a method ofindicating a current value using a label, an inscription, or the like,or a method of indicating the current value on a display portion 110 bsuch as an LED so that an operator can easily grasp a current settingvalue.

Setting portions 110 are respectively provided on both left and rightsides of a surface on a side facing the handle 11 in the substrateaccommodating portion 111 provided on the rear surface side of the screwaccommodating portion 6.

Accordingly, when the fastening tool 1 is viewed from the rear side, thesetting portion 110 can be visually recognized from both left and rightsides of the handle 11.

In a use mode in which the handle 11 is held by hand, a surface of thescrew accommodating portion 6 on a side facing the handle 11 faces theoperator holding the fastening tool 1. Accordingly, in the substrateaccommodating portion 111 provided on the rear surface side of the screwaccommodating portion 6, the setting portion 110 is provided on thesurface on the side facing the handle 11, so that the display portion110 b provided on the setting portion 110 is easily visible. Therefore,it is possible to reduce a possibility that the operator overlooksdisplay. Contents displayed on the display portion 110 b include, inaddition to a setting value of a screw depth defined by the forwardmovement amount of the driver bit 2, an ON or OFF state of a powersupply, an operation mode selected from various selectable operationmodes, presence or absence of a screw, a remaining amount of screws,presence or absence of an abnormality, and the like.

In the use mode in which the handle 11 is held by hand, the operationportion 110 a such as a button provided on the setting portion 110 isalso easily visible. Therefore, in a state in which the handle 11 isheld by one hand, the operation portion 110 a can be operated by theother hand while the operation portion 110 a is visually recognized, andan operation can be reliably performed.

Further, a substrate forming the control unit 100 is accommodated in thesubstrate accommodating portion 111. By mounting switches and the likeforming the operation portion 110 a and lamps and the like forming thedisplay portion 110 b on a surface of the substrate facing the handle11, a substrate for the setting portion 110, separately from the controlunit 100, can be omitted.

FIG. 12 is a block diagram showing an example of the fastening toolaccording to the present embodiment. As described above, the fasteningtool 1 includes the second drive unit 5 that moves the driver bit 2 inthe front-rear direction along the axial direction, and the second driveunit 5 is driven by the bit movement motor 50. The holding member 30 towhich the driver bit 2 is attached is connected to the moving member 32,and the moving member 32 is connected to the pulley 52, which is drivenand rotated by the bit movement motor 50, by the wire 54. The holdingmember 30 and the moving member 32 are configured to move in the forwarddirection along the axial direction of the driver bit 2 along therotation guide member 31.

Accordingly, the control unit 100 can control the movement amount(forward movement amount) of the driver bit 2 by controlling the numberof rotations of the bit movement motor 50. That is, by rotating the bitmovement motor 50 in conjunction with rotation of the bit rotation motor40 that rotates the driver bit 2 in the direction of fastening the screw200, it is possible to control the forward movement amount of the driverbit 2 that moves forward following the screw 200 with fastening of thescrew 200 by the number of rotations of the bit movement motor 50, andto control the stop position of the driver bit 2 along the axialdirection.

The control unit 100 sets, by the setting portion 110, the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2. Further, the control unit 100 controls,based on a combination of ON/OFF of the contact switch portion 84 andON/OFF of the trigger switch portion 90, whether the bit movement motor50 of the second drive unit 5 and the bit rotation motor 40 of the firstdrive unit 4 are driven.

Operation Example of Fastening Tool According to Present Embodiment

FIG. 13A is a side cross-sectional view showing an example of anoperation of the fastening tool according to the present embodiment.FIG. 13B is a top cross-sectional view showing an example of theoperation of the fastening tool according to the present embodiment.FIG. 14 is a flowchart showing an example of the operation of thefastening tool according to the present embodiment. Next, a fasteningoperation of the fastening tool according to the present embodiment willbe described with reference to the drawings.

In a standby state of the fastening tool 1, as shown in FIG. 1A, a tipend of the driver bit 2 is positioned at a standby position P1 on a rearside of the injection passage 80, and the screw 200 can be supplied tothe injection passage 80.

In step SA1 of FIG. 14 , the control unit 100 sets the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2 based on a setting value selected by thesetting portion 110. When the contact member 81 is pressed against thefastening target, the contact switch portion 84 is pressed by thecontact arm 82, the contact switch portion 84 is turned on in step SA2,the trigger 9 is operated, and the trigger switch portion 90 is turnedon in step SA3, the control unit 100 drives the bit rotation motor 40 ofthe first drive unit 4 in step SA4, and drives the bit movement motor 50of the second drive unit 5 in step SA5.

When the bit movement motor 50 is driven to rotate in a positivedirection, which is one direction, the pulley 52 rotates in the positivedirection, so that the wire 54 is wound around the pulley 52. When thewire 54 is wound around the pulley 52, the second moving member 32 cconnected to the wire 54 is guided by the rotation guide member 31 andmoves in the forward direction along the axial direction. When thesecond moving member 32 c moves in the forward direction, the firstmoving member 32 a is pressed by the second moving member 32 c via thebearing 32 b, and moves in the forward direction along the axialdirection together with the second moving member 32 c while compressingthe biasing member 33.

When the first moving member 32 a moves in the forward direction, theholding member 30 connected to the first moving member 32 a by theconnecting member 30 b moves in the forward direction along the axialdirection of the driver bit 2 with the connecting member 30 b guided bythe groove portion 31 a of the rotation guide member 31.

Accordingly, the driver bit 2 held by the holding member 30 moves in theforward direction indicated by the arrow A1, engages with the screw 200supplied to the injection port 81 a of the nose portion 8, moves thescrew 200 in the forward direction, and presses the screw 200 againstthe fastening target.

When the bit rotation motor 40 is driven to rotate in the positivedirection, which is the one direction, the rotation guide member 31rotates in the positive direction. When the rotation guide member 31rotates in the positive direction, the connecting member 30 b connectedto the holding member 30 is pressed by the groove portion 31 a of therotation guide member 31, so that the holding member 30 rotates togetherwith the rotation guide member 31.

Accordingly, the driver bit 2 held by the holding member 30 rotates thescrew 200 in the positive direction (clockwise) and screws the screw 200into the fastening target. The control unit 100 moves the driver bit 2in the forward direction by the second drive unit 5 in conjunction withan operation of rotating the driver bit 2 by the first drive unit 4 toscrew the screw into the fastening target based on a load applied to thebit rotation motor 40, the number of rotations of the bit rotation motor40, a load applied to the bit movement motor 50, the number of rotationsof the bit movement motor 50, and the like, thereby causing the driverbit 2 to follow the screw to be screwed into the fastening target. Inthe present embodiment, the load applied to the bit rotation motor 40 orthe like is a force based on resistance including a frictional force orthe like generated between the screw 200 and the fastening target whenthe screw 200 is screwed into the fastening target.

When the control unit 100 determines that the number of rotations of thebit movement motor 50 reaches the setting value selected by the settingportion 110 in step SA6 and the tip end of the driver bit 2 reaches aset operation end position P2 as shown in FIGS. 13A and 13B, the controlunit 100 stops driving of the bit rotation motor 40 in step SA7, stopsrotation of the bit movement motor 50 in the positive direction in stepSA8, and then reversely rotates the bit movement motor 50 in step SA9.

When the bit movement motor 50 rotates in a reverse direction, which isanother direction, the pulley 52 rotates in the reverse direction, sothat the wire 54 is pulled out from the pulley 52. When the wire 54 ispulled out from the pulley 52, the second moving member 32 c moves inthe forward direction, so that the compressed biasing member 33 extendsand presses the second moving member 32 c in the rearward direction.

The second moving member 32 c is pressed rearward by the biasing member33, thereby being guided by the rotation guide member 31 and movingrearward along the axial direction. When the second moving member 32 cmoves in the rearward direction, the first moving member 32 a is pulledby the second moving member 32 c via the bearing 32 b, and moves in therearward direction along the axial direction together with the secondmoving member 32 c.

When the first moving member 32 a moves in the rearward direction, theholding member 30 connected to the first moving member 32 a by theconnecting member 30 b moves in the rearward direction along the axialdirection of the driver bit 2 with the connecting member 30 b guided bythe groove portion 31 a of the rotation guide member 31.

When the bit movement motor 50 rotates reversely to an initial positionwhere the wire 54 is pulled out from the pulley 52 by a predeterminedamount and the holding member 30 and the moving member 32 move in therearward direction to a position where the tip end of the driver bit 2returns to the standby position P1 in step SA10, the control unit 100stops the reverse rotation of the bit movement motor 50 in step SA11.

Since the moving member 32 includes the buffer member 32 d made ofrubber or the like on the rear side of the second moving member 32 c, itis possible to prevent the second moving member 32 c from directlyhitting the rear frame 10 c due to movement of the second moving member32 c in the rear direction, and it is possible to prevent occurrence ofsound or damage. When the trigger switch portion 90 is turned off, thecontrol unit 100 rotates the screw feeding motor 70 in one direction tolower the engagement portion 73. When the engagement portion 73 islowered to a position where the engagement portion 73 is engaged withthe next screw 200, the control unit 100 causes the screw feeding motor70 to rotate reversely, thereby raising the engagement portion 73 andsupplying the next screw 200 to the injection passage 80.

FIGS. 15A to 15C are cross-sectional views showing fastening states ofthe screw, in which FIG. 15A shows a so-called flush state in which ahead portion 201 of the screw 200 does not float up from or is notburied in a surface of a fastening target 202, FIG. 15B shows a state inwhich the head portion 201 of the screw 200 floats from the fasteningtarget 202, and FIG. 15C shows a state in which the head portion 201 ofthe screw 200 is buried in the fastening target 202.

In the fastening tool 1, when the tip end of the driver bit 2 reachesthe operation end position P2, in a case where the screw 200 is acountersunk head screw, as shown in FIG. 15A, the forward movementamount of the driver bit 2 is preferably set such that the surface ofthe head portion 201 of the screw 200 is in the so-called flush state inwhich the surface of the head portion 201 is the same as a surface ofthe fastening target 202. The screw 200 is not limited to thecountersunk head screw, and if the screw 200 is a pan head, a bind, atruss, or the like, it is preferable that the forward movement amount ofthe driver bit 2 is set so that a seating surface of the head portion201 of the screw 200 contacts the surface of the fastening target 202and the head portion 201 of the screw 200 does not float from thefastening target 202.

When the tip end of the driver bit 2 reaches the operation end positionP2, if the head portion 201 of the screw 200 is in a state of floatingfrom the fastening target 202 as shown in FIG. 15B, the movement amount(forward movement amount) of the driver bit 2 is set by the settingportion 110, and the forward movement amount of the driver bit 2 isincreased by increasing the number of rotations (rotation amount) of thebit movement motor 50, and the operation end position P2 is movedforward. On the other hand, when the head portion 201 of the screw 200is in a state of being buried in the fastening target 202 as shown inFIG. 15C, the movement amount (forward movement amount) of the driverbit 2 is set by the setting portion 110, and the forward movement amountof the driver bit 2 is decreased by decreasing the number of rotationsof the bit movement motor 50, and the operation end position P2 isretreated.

As described above, the movement amount (forward movement amount) of thedriver bit 2 is defined by the number of rotations of the bit movementmotor 50. The bit movement motor 50 is rotated by the number ofrotations set by the setting portion 110 starting from the standbyposition P1, which is an initial position of the driver bit 2, and thenthe rotation of the bit movement motor 50 is stopped or reversed, sothat the operation end position P2 is controlled. Therefore, atightening depth can be adjusted.

Thus, in order to make it possible to advance a tip end position of thedriver bit 2 held by the holding member 30 by a predetermined amountbased on the number of rotations of the bit movement motor 50 withreference to the predetermined standby position P1, a standby positionof the holding member 30 to which the driver bit 2 is attached and themoving member 32 that moves the holding member 30 is set. An operationof setting the standby position of the holding member 30 and the movingmember 32 is referred to as a first initialization operation.

The holding member 30 and the moving member 32 are moved to the setstandby position before start of driving and fastening operations, and aposition of the holding member 30 and the moving member 32 is controlledby the number of rotations of the bit movement motor 50 with referenceto the standby position. The holding member 30 and the moving member 32are moved forward from the set standby position by a predeterminedmovement amount (forward movement amount) to perform the fasteningoperation. An operation of moving the holding member 30 and the movingmember 32 to the standby position set in the first initializationoperation is referred to as a second initialization operation.

It is conceivable that, as the setting unit that sets the standbyposition of the holding member 30 and the moving member 32 in the firstinitialization operation, a sensor is used, or a maximum position in arange in which the holding member 30 and the moving member 32 can moveforward and rearward is used as a reference. When the sensor is used, adetection position of the sensor or a position moved from the detectionposition by a specified amount is set as the standby position.

When the maximum position in the range in which the holding member 30and the moving member 32 can move forward and rearward is used, aposition obtained by moving the holding member 30 and the moving member32 from a front end position or a rear end position by a specifiedamount is set as the standby position.

FIGS. 16A to 16D are diagrams showing examples of an operation ofsetting the standby position of the holding member and the moving memberin the first initialization operation. Next, the operation of settingthe standby position of the holding member 30 and the moving member 32will be described. FIGS. 16A to 16D show the examples of the operationof setting the standby position of the holding member 30 and the movingmember 32 using the maximum position in the range in which the holdingmember 30 and the moving member 32 can move forward and rearward.

As shown in FIG. 16A, the control unit 100 rotates the bit movementmotor 50 in the positive direction, which is the one direction, from astate in which the holding member 30 and the moving member 32 are at adesired position. When the bit movement motor 50 rotates forward, thewire 54 is wound around the pulley 52, so that the moving member 32 andthe holding member 30 connected to the moving member 32 move in theforward direction along the axial direction of the driver bit 2 alongthe rotation guide member 31.

As shown in FIG. 16B, when the bit movement motor 50 rotates forwarduntil the holding member 30 and the moving member 32 move to a front endposition PF that is one end position, the control unit 100 stops theforward rotation of the bit movement motor 50 and moves the holdingmember 30 and the moving member 32 to the front end position PF.

Next, the control unit 100 rotates the bit movement motor 50 in thereverse direction, which is the other direction. When the bit movementmotor 50 rotates reversely, the wire 54 is pulled out from the pulley52, so that the moving member 32 is pressed in the rearward direction bythe biasing member 33, and the moving member 32 and the holding member30 connected to the moving member 32 move in the rearward directionalong the axial direction of the driver bit 2 along the rotation guidemember 31.

As shown in FIG. 16C, when the bit movement motor 50 rotates reverselyuntil the holding member 30 and the moving member 32 move to a rear endposition PE that is another end position, the control unit 100 stops thereverse rotation of the bit movement motor 50 and moves the holdingmember 30 and the moving member 32 to the rear end position PE bybiasing of the biasing member 33.

The control unit 100 acquires a movement amount of the holding member 30and the moving member 32 from the front end position PF to the rear endposition PE as a total distance L1. The movement amount from the frontend position PF to the rear end position PE is obtained from the numberof rotations of the bit movement motor 50.

In the control unit 100, a movement amount of the holding member 30 andthe moving member 32 from the standby position to the front end positionPF is set in advance as a target movement amount L2. The control unit100 sets a standby position movement amount L3 to a difference betweenthe total distance L1 from the front end position PF to the rear endposition PE and the target movement amount L2 set in advance, and storesthe standby position movement amount L3. The standby position movementamount L3 is a movement amount of the holding member 30 and the movingmember 32 from the rear end position PE.

As shown in FIG. 16D, the control unit 100 rotates the bit movementmotor 50 forward to move the holding member 30 and the moving member 32in the forward direction from the rear end position PE. When the bitmovement motor 50 is rotated forward at the number of rotationscorresponding to the standby position movement amount L3, the controlunit 100 stops the forward rotation of the bit movement motor 50, movesthe holding member 30 and the moving member 32 to the standby position,and moves the tip end of the driver bit 2 held by the holding member 30to the standby position P1.

When the holding member 30 and the moving member 32 are moved to thefront end position PF and the rear end position PE, it is desirable todrive the holding member 30 and the moving member 32 at a low speed thatdoes not affect durability of a tool, for example, when the secondmoving member 32 c hits the buffer member 32 d.

FIGS. 17A to 17C are diagrams showing examples of an operation of movingthe holding member and the moving member to the standby position in thesecond initialization operation. Next, the operation of moving theholding member 30 and the moving member 32 to the standby position setin advance will be described.

As shown in FIG. 17A, the control unit 100 rotates the bit movementmotor 50 in the reverse direction, which is the other direction, from astate in which the holding member 30 and the moving member 32 are at adesired position. When the bit movement motor 50 rotates reversely, thewire 54 is pulled out from the pulley 52, so that the moving member 32is pressed in the rearward direction by the biasing member 33, and themoving member 32 and the holding member 30 connected to the movingmember 32 move in the rearward direction along the axial direction ofthe driver bit 2 along the rotation guide member 31.

As shown in FIG. 17B, when the bit movement motor 50 rotates reverselyuntil the holding member 30 and the moving member 32 move to the rearend position PE, the control unit 100 stops the reverse rotation of thebit movement motor 50 and moves the holding member 30 and the movingmember 32 to the rear end position PE by biasing of the biasing member33.

As shown in FIG. 17C, the control unit 100 rotates the bit movementmotor 50 forward to move the holding member 30 and the moving member 32in the forward direction from the rear end position PE. When the bitmovement motor 50 is rotated forward at the number of rotationscorresponding to the standby position movement amount L3, the controlunit 100 stops the forward rotation of the bit movement motor 50, movesthe holding member 30 and the moving member 32 to the standby position,and moves the tip end of the driver bit 2 held by the holding member 30to the standby position P1.

In the first initialization operation described with reference to FIGS.16A to 16D, an operation of setting the standby position of the holdingmember 30 and the moving member 32 is executed in a factory, forexample, at the time of shipment of a product without depending on anoperation of a user, and the standby position movement amount L3 isstored in advance.

On the other hand, in the second initialization operation described withreference to FIGS. 17A to 17C, an operation of moving the holding member30 and the moving member 32 to the standby position based on the standbyposition movement amount L3 is preferably performed every time a powersupply of the fastening tool 1 is turned on so that a stable fasteningoperation can be performed.

Therefore, the first initialization operation and the secondinitialization operation, which are initialization operations related tothe standby position of the holding member 30 and the moving member 32,can be selected.

FIG. 18 is a flowchart showing an example of an operation of selectingthe first initialization operation and the second initializationoperation.

When the power supply is turned on in step SB1 of FIG. 18 , the controlunit 100 selects an initialization operation to be executed in step SB2.When the control unit 100 selects execution of the first initializationoperation, in step SB3, the control unit 100 executes the firstinitialization operation described above with reference to FIGS. 16A to16D and sets the standby position of the holding member 30 and themoving member 32. When the control unit 100 selects execution of thesecond initialization operation, in step SB4, the control unit 100executes the second initialization operation described above withreference to FIGS. 17A to 17C and moves the holding member 30 and themoving member 32 to the standby position based on the standby positionmovement amount L3. After executing the second initialization operation,the control unit 100 executes a normal fastening operation in step SB5according to the flowchart of FIG. 14 described above.

As described above, in the first initialization operation, the holdingmember 30 and the moving member 32 are moved at a low speed from thefront end position PF to the rear end position PE, the total distance L1from the front end position PF to the rear end position PE is acquired,a movement amount from the rear end position PE, which is determined sothat a movement amount from the front end position PF becomes thepredetermined target movement amount L2, is set as the standby positionmovement amount L3, and the standby position movement amount L3 isrecorded in a memory on the substrate (not shown) forming the controlunit 100. Accordingly, various variations of a machine, such as adifference in dimension within a range of tolerance, can be eliminated,and the standby position of the holding member 30 and the moving member32 can be set to, for example, a constant position from the front endposition PF.

In the second initialization operation, the holding member 30 and themoving member 32 are moved from the rear end position PE to the standbyposition according to the standby position movement amount L3 every timethe power supply is turned on for use by the user, so that the movementamount of the holding member 30 and the moving member 32 can beminimized. Further, in the second initialization operation, the secondinitialization operation can be executed in a state where the tip end ofthe driver bit 2 is positioned at the standby position P1 on the rearside of the injection passage 80 and the screw 200 is supplied to theinjection passage 80.

As described above, the movement amount (forward movement amount) of thedriver bit 2 is defined by the number of rotations of the bit movementmotor 50 starting from the standby position of the holding member 30 andthe moving member 32, that is, the standby position P1 of the driver bit2. Therefore, when the standby position of the holding member 30 and themoving member 32, that is, the standby position P1 of the driver bit 2varies, the tightening depth set by the setting portion 110 varies.

On the other hand, by performing the second initialization operationevery time the power supply is turned on, it is possible to accuratelyadjust the tightening depth of the screw by the operation of rotatingthe bit movement motor 50 by the number of rotations set by the settingportion 110 starting from the standby position of the holding member 30and the moving member 32, that is, the standby position P1 of the driverbit 2.

FIG. 19 is a flowchart showing a modification of the operation of thefastening tool according to the present embodiment. FIG. 20 is a graphshowing a relationship between output of the contact switch portion andcontrol over the bit rotation motor and the bit movement motor. Next,another example of the fastening operation of the fastening toolaccording to the present embodiment will be described with reference tothe drawings. In this modification, the bit rotation motor 40 and thebit movement motor 50 are controlled by detecting whether the fasteningtool 1 floats up with respect to the fastening target from the output ofthe contact switch portion 84.

In the standby state of the fastening tool 1, as shown in FIG. 1A, thetip end of the driver bit 2 is positioned at the standby position P1 onthe rear side of the injection passage 80, and the screw 200 can besupplied to the injection passage 80.

In step SC1 of FIG. 19 , the control unit 100 sets the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2 based on a setting value selected by thesetting portion 110. When the contact member 81 is pressed against thefastening target, the contact switch portion 84 is pressed by thecontact arm 82, the contact switch portion 84 is turned on in step SC2,the trigger 9 is operated, and the trigger switch portion 90 is turnedon in step SC3, the control unit 100 drives the bit rotation motor 40 ofthe first drive unit 4 in step SC4, and drives the bit movement motor 50of the second drive unit 5 in step SC5.

When the bit movement motor 50 is driven to rotate in the positivedirection, which is the one direction, the pulley 52 rotates in thepositive direction, so that the wire 54 is wound around the pulley 52,and the moving member 32 in which the second moving member 32 c isconnected to the wire 54 and the holding member 30 connected to themoving member 32 by the first moving member 32 a move in the forwarddirection.

Accordingly, the driver bit 2 held by the holding member 30 moves in theforward direction indicated by the arrow A1, engages with the screw 200supplied to the injection port 81 a of the nose portion 8, moves thescrew 200 in the forward direction, and presses the screw 200 againstthe fastening target.

When the bit rotation motor 40 is driven to rotate in the positivedirection, which is the one direction, the holding member 30 rotatestogether with the rotation guide member 31.

Accordingly, the driver bit 2 held by the holding member 30 rotates thescrew 200 in the positive direction (clockwise) and screws the screw 200into the fastening target. The control unit 100 moves the driver bit 2in the forward direction by the second drive unit 5 in conjunction withan operation of rotating the driver bit 2 by the first drive unit 4 toscrew the screw into the fastening target based on a load applied to thebit rotation motor 40, the number of rotations of the bit rotation motor40, a load applied to the bit movement motor 50, the number of rotationsof the bit movement motor 50, and the like, thereby causing the driverbit 2 to follow the screw to be screwed into the fastening target.

When the control unit 100 determines in step SC6 that the number ofrotations of the bit movement motor 50 reaches the setting valueselected by the setting portion 110 and the tip end of the driver bit 2reaches the set operation end position P2, the control unit 100 stopsdriving of the bit movement motor 50 in step SC7.

When the control unit 100 stops driving of the bit movement motor 50 instep SC7, the control unit 100 determines whether the contact switchportion 84 is turned on in step SC8. When the contact switch portion 84is turned on, the control unit 100 determines that the fastening tool 1does not float up in the direction away from the fastening target, stopsrotation of the bit rotation motor 40 in the positive direction in stepSC9, and rotates the bit movement motor 50 reversely in step SC10 inorder to end the fastening operation.

When the bit movement motor 50 rotates in the reverse direction, whichis the other direction, the pulley 52 rotates in the reverse direction,so that the wire 54 is pulled out from the pulley 52, and the movingmember 32 in which the second moving member 32 c is pressed by thebiasing member 33 and the holding member 30 connected to the movingmember 32 by the first moving member 32 a move in the rearwarddirection.

When the bit movement motor 50 rotates reversely to an initial positionwhere the wire 54 is pulled out from the pulley 52 by a predeterminedamount and the holding member 30 and the moving member 32 move in therearward direction to a position where the tip end of the driver bit 2returns to the standby position P1 in step SC11, the control unit 100stops the reverse rotation of the bit movement motor 50 in step SC12.

When the contact switch portion 84 is turned off in step SC8, thecontrol unit 100 determines that the fastening tool 1 floats up in thedirection away from the fastening target, and continues driving forrotating the bit rotation motor 40 in the positive direction in a statewhere driving of the bit movement motor 50 is stopped.

Accordingly, the driver bit 2 held by the holding member 30 rotates thescrew 200 in the positive direction and further screws the screw 200into the fastening target, so that the fastening tool 1 moves in adirection approaching the fastening target. Therefore, the fasteningtool 1 moves relative to the contact arm 82, and the contact switchportion 84 is pressed by the contact arm 82, and the contact switchportion 84 is turned on. When the contact switch portion 84 is turnedon, the control unit 100 executes processing of steps SC9 to SC12described above in order to end the fastening operation, and performsoperations of stopping the bit rotation motor 40 and returning thedriver bit 2 to the standby position by the reverse rotation of the bitmovement motor 50.

In a state in which the contact switch portion 84 is turned off anddriving of the bit movement motor 50 is stopped, by performing controlcalled a braking operation in which the bit movement motor 50 does notrotate by an external force during an operation of rotating the bitrotation motor 40 in the positive direction, the control unit 100maintains a state in which the holding member 30, the moving member 32,and the driver bit 2 held by the holding member 30 are stopped at theoperation end position P2.

However, in a state in which driving of the bit movement motor 50 isstopped, during the operation of rotating the bit rotation motor 40 inthe positive direction, the screw 200 is tightened while a force isapplied in a direction of pressing the fastening tool 1 against thefastening target by the operator. Therefore, even when the brakingoperation is performed on the bit movement motor 50, the holding member30, the moving member 32, and the driver bit 2 held by the holdingmember 30 may move in the rearward direction from the operation endposition P2 due to a force applied by the operator.

Therefore, the control unit 100 detects presence or absence of reverserotation of the bit movement motor 50 in step SC13, and when the reverserotation of the bit movement motor 50 is detected, the control unit 100returns to step SCS, rotates the bit movement motor 50 forward, movesthe holding member 30 and the moving member 32 in the forward direction,and returns the driver bit 2 to the operation end position P2. Then, theforward rotation of the bit movement motor 50 is stopped, and thebraking operation is performed.

In order to switch ON or OFF the contact switch portion 84 by thecontact arm 82, it is necessary to move the contact arm 82 by apredetermined amount. Therefore, as described above, it is detected thatthe contact switch portion 84 is OFF in step SC8, and in a state inwhich the driving of the bit movement motor 50 is stopped, the drivingof rotating the bit rotation motor 40 in the positive direction iscontinued, and the position of the holding member 30 and the movingmember 32 may fluctuate while the contact arm 82 moves until the contactswitch portion 84 is switched from OFF to ON. Therefore, it is desirableto provide a detection unit that detects a position of the contact arm82. Rotation of the bit holding portion 3 and movement of the bitholding portion 3 in the axial direction may be performed by a singlemotor. The control unit 100 may control a timing of stopping driving ofthe single motor based on presence or absence of an operation of thecontact switch portion 84.

FIG. 21 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment. FIGS. 22A and22B are graphs showing relationships between loads and control over thebit rotation motor. Next, the other modification of the fasteningoperation of the fastening tool according to the present embodiment willbe described with reference to the drawings. In this modification, aload applied to the bit rotation motor 40 is detected to control the bitrotation motor 40.

In the standby state of the fastening tool 1, as shown in FIG. 1A, thetip end of the driver bit 2 is positioned at the standby position P1 onthe rear side of the injection passage 80, and the screw 200 can besupplied to the injection passage 80.

In step SD1 of FIG. 21 , the control unit 100 sets the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2 based on a setting value selected by thesetting portion 110. When the contact member 81 is pressed against thefastening target, the contact switch portion 84 is pressed by thecontact arm 82, the contact switch portion 84 is turned on in step SD2,the trigger 9 is operated, and the trigger switch portion 90 is turnedon in step SD3, the control unit 100 drives the bit rotation motor 40 ofthe first drive unit 4 in step SD4, and drives the bit movement motor 50of the second drive unit 5 in step SDS.

When the bit movement motor 50 is driven to rotate in the positivedirection, which is the one direction, the pulley 52 rotates in thepositive direction, so that the wire 54 is wound around the pulley 52,and the moving member 32 in which the second moving member 32 c isconnected to the wire 54 and the holding member 30 connected to themoving member 32 by the first moving member 32 a move in the forwarddirection.

Accordingly, the driver bit 2 held by the holding member 30 moves in theforward direction indicated by the arrow A1, engages with the screw 200supplied to the injection port 81 a of the nose portion 8, moves thescrew 200 in the forward direction, and presses the screw 200 againstthe fastening target.

When the bit rotation motor 40 is driven to rotate in the positivedirection, which is the one direction, the holding member 30 rotatestogether with the rotation guide member 31.

Accordingly, the driver bit 2 held by the holding member 30 rotates thescrew 200 in the positive direction (clockwise) and screws the screw 200into the fastening target. The control unit 100 moves the driver bit 2in the forward direction by the second drive unit 5 in conjunction withan operation of rotating the driver bit 2 by the first drive unit 4 toscrew the screw into the fastening target based on a load applied to thebit rotation motor 40, the number of rotations of the bit rotation motor40, a load applied to the bit movement motor 50, the number of rotationsof the bit movement motor 50, and the like, thereby causing the driverbit 2 to follow the screw to be screwed into the fastening target.

In step SD6, the control unit 100 determines whether the number ofrotations of the bit movement motor 50 reaches the setting valueselected by the setting portion 110 and the tip end of the driver bit 2reaches the set operation end position P2. When it is determined thatthe number of rotations of the bit movement motor 50 does not reach thesetting value selected by the setting portion 110, the control unit 100detects a load applied to the bit rotation motor 40 in step SD7, andwhen the control unit 100 detects a predetermined load, the control unit100 controls the bit rotation motor 40 in step SD8.

A rotation speed of the driver bit 2 differs depending on a magnitude ofthe load applied to the bit rotation motor 40. If a current value and avoltage value applied to the bit rotation motor 40 are the same, thehigher the load applied to the bit rotation motor 40, the lower therotation speed. Therefore, the control unit 100, as a fluctuationdetection unit that detects a factor causing a fluctuation in a rotationspeed of the bit rotation motor 40, detects a load applied to the bitrotation motor 40, and decreases output of the bit rotation motor 40,such as decreasing a voltage value applied to the bit rotation motor 40or decreasing a current value applied to the bit rotation motor 40, asthe load applied to the bit rotation motor 40 is low, as compared with acase where the load is high. For example, a threshold value serving as areference for determining the magnitude of the load may be set inadvance. When the detected load applied to the bit rotation motor 40 isequal to or more than the threshold value, the voltage value, thecurrent value, or output of the bit rotation motor 40 or the like may becontrolled to be decreased, and when the detected load applied to thebit rotation motor 40 is less than the threshold value, the voltagevalue, the current value, or the output of the bit rotation motor 40 orthe like may be controlled to be increased.

Accordingly, when the load applied to the bit rotation motor 40 is low,the rotation speed of the bit rotation motor 40 is decreased, therebypreventing an increase in the rotation speed as compared with the casewhere the load is high, and preventing a difference in the rotationspeed of the bit rotation motor 40 due to the magnitude of the loadapplied to the bit rotation motor 40. Therefore, occurrence of variationin a speed at which the screw 200 is fastened is prevented.

When the control unit 100 determines that the number of rotations of thebit movement motor 50 reaches the setting value selected by the settingportion 110 and the tip end of the driver bit 2 reaches the setoperation end position P2 in step SD6, the control unit 100 stopsdriving of the bit rotation motor 40 in step SD9, stops rotation of thebit movement motor 50 in the positive direction in step SD10, and thenreversely rotates the bit movement motor 50 in step SD11.

When the bit movement motor 50 rotates in the reverse direction, whichis the other direction, the pulley 52 rotates in the reverse direction,so that the wire 54 is pulled out from the pulley 52, and the movingmember 32 in which the second moving member 32 c is pressed by thebiasing member 33 and the holding member 30 connected to the movingmember 32 by the first moving member 32 a move in the rearwarddirection.

When the bit movement motor 50 rotates reversely to an initial positionwhere the wire 54 is pulled out from the pulley 52 by a predeterminedamount and the holding member 30 and the moving member 32 move in therearward direction to a position where the tip end of the driver bit 2returns to the standby position P1 in step SD12, the control unit 100stops the reverse rotation of the bit movement motor 50 in step SD13.

In control for decreasing output of the bit rotation motor 40, as shownin FIG. 22A, after a predetermined load is detected, the output may bedecreased so that the rotation speed becomes constant until the bitrotation motor 40 rotates at the number of rotations for moving thedriver bit 2 to the operation end position. As shown in FIG. 22B, afterthe predetermined load is detected, the output may be graduallydecreased so as to reach a target rotation speed until the bit rotationmotor 40 rotates at the number of rotations for moving the driver bit 2to the operation end position.

A fluctuation in a power supply voltage causes a difference in therotation speed of the driver bit 2, and the lower the power supplyvoltage, the lower the rotation speed. Therefore, the control unit 100,as the fluctuation detection unit that detects a factor causing afluctuation in the rotation speed of the bit rotation motor 40, detectsthe power supply voltage, and decreases the output of the bit rotationmotor 40 as the power supply voltage is high, as compared with a casewhere the power supply voltage is low.

Accordingly, when the power supply voltage is high, the rotation speedof the bit rotation motor 40 is decreased as compared with a case wherethe power supply voltage is low, so that occurrence of a difference inthe rotation speed of the bit rotation motor 40 due to a fluctuation inthe power supply voltage is prevented. Therefore, occurrence ofvariation in the speed at which the screw 200 is fastened is prevented.

The control unit 100 may set the target rotation speed of the bitrotation motor 40, detect the rotation speed of the bit rotation motor40, compare the detected rotation speed of the bit rotation motor 40with the target rotation speed of the bit rotation motor 40 set inadvance, and control the bit rotation motor 40 so as to achieve thetarget rotation speed.

If the rotation speed of the bit rotation motor 40 is decreased, itbecomes a factor that a working speed of fastening the screw to thefastening target is decreased. On the other hand, during a stopprocessing of the bit rotation motor 40 after the screw is tightened toa target screw tightening depth set by the setting portion 110, thescrew is tightened to the fastening target by rotation of the driver bit2 until rotation of the bit rotation motor 40 is completely stopped.Therefore, the faster the rotation speed of the bit rotation motor 40immediately before the rotation is stopped, the more the screw istightened beyond the target.

Thus, a factor that a quality of a screw tightening operation isdecreased due to the difference in the rotation speed of the bitrotation motor 40 is the rotation speed immediately before the rotationof the bit rotation motor 40 is stopped. Therefore, if the rotationspeed of the bit rotation motor 40 is constant, without an influence ofa load, immediately before the movement amount (forward movement amount)of the holding member 30 and the moving member 32 reaches the targetscrew tightening depth set by the setting portion 110, a desired effectcan be obtained.

The load applied to the bit rotation motor 40 increases when tighteningof the screw to the fastening target is started, but the load fluctuatesdepending on a material of the fastening target and the like. Therefore,after the detection of the load described above for controlling therotation speed of the bit rotation motor 40, control over the rotationspeed of the bit rotation motor 40 described above based on the load,the power supply voltage, and the like is executed until the targetscrew tightening depth is reached.

A timekeeping unit is provided. The control unit 100 may control therotation speed of the bit rotation motor 40 based on the load, the powersupply voltage, and the like after a predetermined time elapses fromstart of driving of the bit rotation motor 40 (forward rotation). Aposition detection unit that detects the position of the holding member30 and the moving member 32 may be provided. After the position of theholding member 30 and the moving member 32 reaches a predeterminedposition, the above control over the rotation speed of the bit rotationmotor 40 based on the load, the power supply voltage, and the like maybe executed. The predetermined position of the holding member 30 and themoving member 32 at which the control over the rotation speed of the bitrotation motor 40 is executed is set between a position where the aboveload is detected and a position where the target screw tightening depthis reached for controlling the rotation speed of the bit rotation motor40.

In a method of setting the target rotation speed of the bit rotationmotor 40 and controlling output, it is considered that the target screwtightening depth is reached before the rotation speed of the bitrotation motor 40 is decreased to the target rotation speed due to aninfluence of a length of a control execution section or the like.Therefore, during control of decreasing the rotation speed of the bitrotation motor 40 to the target rotation speed, braking control over thebit rotation motor 40 may be performed. For example, when a deviationbetween the target rotation speed of the bit rotation motor 40 and adetected actual rotation speed is large, the braking control over thebit rotation motor 40 may be performed until the deviation between theactual rotation speed and the target rotation speed falls within aspecified range, and when the deviation falls within the specifiedrange, the control of decreasing the rotation speed of the bit rotationmotor 40 to the target rotation speed may be performed.

Further, if the driver bit 2 and the screw are disengaged after thedriver bit 2 reaches the target screw tightening depth, the screw is nottightened any more even if the driver bit 2 rotate. Therefore, after thedriver bit 2 moves forward until the driver bit 2 reaches the targetscrew tightening depth, the bit movement motor 50 may be rotatedreversely before the rotation of the bit rotation motor 40 is stopped.The rotation of the bit holding portion 3 and the movement of the bitholding portion 3 in the axial direction may be performed by a singlemotor. The control unit 100 may detect a factor that causes a rotationspeed of the motor to fluctuate, such as a load applied to the singlemotor, and control the motor.

FIG. 23 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment. FIG. 24A is agraph showing a relationship between rotation speeds of the bit rotationmotor and the bit movement motor under feedback (FB) control. FIG. 24Bis a graph showing a relationship between a moving speed of the screw bythe rotation of the bit rotation motor and a moving speed of the driverbit by the bit movement motor under the feedback (FB) control. Next, theother modification of the fastening operation of the fastening toolaccording to the present embodiment will be described with reference tothe drawings. In this modification, the moving speed of the screw by therotation of the bit rotation motor 40 and the moving speed of the driverbit by the bit movement motor 50 are synchronized by the feedbackcontrol.

In the standby state of the fastening tool 1, as shown in FIG. 1A, thetip end of the driver bit 2 is positioned at the standby position P1 onthe rear side of the injection passage 80, and the screw 200 can besupplied to the injection passage 80.

In step SE1 of FIG. 23 , the control unit 100 sets the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2 based on a setting value selected by thesetting portion 110. When the contact member 81 is pressed against thefastening target, the contact switch portion 84 is pressed by thecontact arm 82, the contact switch portion 84 is turned on in step SE2,the trigger 9 is operated, and the trigger switch portion 90 is turnedon in step SE3, the control unit 100 drives the bit rotation motor 40 ofthe first drive unit 4 in step SE4, and drives the bit movement motor 50of the second drive unit 5 in step SE5.

When the bit movement motor 50 is driven to rotate in the positivedirection, which is the one direction, the pulley 52 rotates in thepositive direction, so that the wire 54 is wound around the pulley 52,and the moving member 32 in which the second moving member 32 c isconnected to the wire 54 and the holding member 30 connected to themoving member 32 by the first moving member 32 a move in the forwarddirection.

Accordingly, the driver bit 2 held by the holding member 30 moves in theforward direction indicated by the arrow A1, engages with the screw 200supplied to the injection port 81 a of the nose portion 8, moves thescrew 200 in the forward direction, and presses the screw 200 againstthe fastening target.

When the bit rotation motor 40 is driven to rotate in the positivedirection, which is the one direction, the holding member 30 rotatestogether with the rotation guide member 31.

Accordingly, the driver bit 2 held by the holding member 30 rotates thescrew 200 in the positive direction (clockwise) and screws the screw 200into the fastening target. The control unit 100 moves the driver bit 2in the forward direction by the second drive unit 5 in conjunction withan operation of rotating the driver bit 2 by the first drive unit 4 toscrew the screw into the fastening target, thereby causing the driverbit 2 to follow the screw to be screwed into the fastening target.

In step SE6, the control unit 100 determines whether the number ofrotations of the bit movement motor 50 reaches the setting valueselected by the setting portion 110 and the tip end of the driver bit 2reaches the set operation end position P2. When it is determined thatthe number of rotations of the bit movement motor 50 does not reach thesetting value selected by the setting portion 110, the control unit 100detects a load applied to the bit movement motor 50 in step SE7, andwhen the control unit 100 detects a predetermined load, the control unit100 acquires a rotation speed of the bit rotation motor 40 and arotation speed of the bit movement motor 50 in step SE8.

In step SE9, the control unit 100 calculates a target rotation speed ofthe bit movement motor 50 based on a gear ratio of the speed reducer ofthe bit rotation motor 40 and the rotation speed of the bit rotationmotor 40 or calculates a target rotation speed of the bit rotation motor40 based on a gear ratio of the speed reducer of the bit movement motor50 and the rotation speed of the bit movement motor 50 so that byfastening the screw 200 to the fastening target by the rotation of thebit rotation motor 40, a moving speed when the screw 200 is moved in theforward direction, a moving speed of the holding member 30 and themoving member 32 which move in the forward direction by the rotation ofthe bit movement motor 50, and the moving speed of the driver bit 2attached to the holding member 30 substantially coincide with oneanother as shown in FIG. 24B.

In step SE10, the control unit 100 controls the bit movement motor 50 inthe present example by the feedback control based on the target rotationspeed of the bit rotation motor 40, the target rotation speed of the bitmovement motor 50, the gear ratio of the speed reducer, and the like.For example, the control is performed by increasing or decreasing PWMoutput to the bit movement motor 50 and adjusting the rotation speed.

When it is determined that the number of rotations of the bit movementmotor 50 reaches the setting value selected by the setting portion 110and the tip end of the driver bit 2 reaches the set operation endposition P2 in step SE6, the control unit 100 stops driving of the bitrotation motor 40 in step SE11, stops rotation of the bit movement motor50 in the positive direction in step SE12, and then reversely rotatesthe bit movement motor 50 in step SE13.

When the bit movement motor 50 rotates in the reverse direction, whichis the other direction, the pulley 52 rotates in the reverse direction,so that the wire 54 is pulled out from the pulley 52, and the movingmember 32 in which the second moving member 32 c is pressed by thebiasing member 33 and the holding member 30 connected to the movingmember 32 by the first moving member 32 a move in the rearwarddirection.

When the bit movement motor 50 rotates reversely to an initial positionwhere the wire 54 is pulled out from the pulley 52 by a predeterminedamount and the holding member 30 and the moving member 32 move in therearward direction to a position where the tip end of the driver bit 2returns to the standby position P1 in step SE14, the control unit 100stops the reverse rotation of the bit movement motor 50 in step SE15.

The feedback control described above is control required after thefastening target and the screw 200 come into contact with each other andloads on the bit rotation motor 40 and the bit movement motor 50fluctuate. Therefore, control when the feedback control is not executedis set as a first control mode, and control when the feedback control isexecuted is set as a second control mode, and the first control mode isexecuted before a predetermined load is detected in one or both of thebit rotation motor 40 and the bit movement motor 50. When thepredetermined load is detected in one or both of the bit rotation motor40 and the bit movement motor 50, the first control mode is switched tothe second control mode, and the second control mode is executed.Accordingly, it is possible to prevent a delay in an operation time.

As a unit that improves responsiveness of the feedback control andimplements more stable work quality, an acceleration or decelerationlimit value for the bit movement motor 50 may be changed when thefeedback control is executed after the load is detected and when thefeedback control is not executed before the load is detected. Normally,when the PWM output is performed to the motor, by limiting anacceleration amount per unit time in order to stabilize the output ofthe motor, control is executed to prevent an acceleration current at thetime of starting in particular from becoming excessive. However, whenthe above feedback control is executed while acceleration is limited atthe time of starting the bit movement motor 50, the PWM output generatedby the feedback control is limited and applied to the bit movement motor50, so that responsiveness to the feedback control is deteriorated.Therefore, during execution of the feedback control, it is desirable toset an acceleration limit amount to be larger than that at the time ofstarting the motor when the feedback control is not executed.

FIG. 25 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment. FIGS. 26A and26B are graphs showing relationships between loads and control over thebit movement motor. Next, the other modification of the fasteningoperation of the fastening tool according to the present embodiment willbe described with reference to the drawings. In this modification, aload applied to the bit movement motor 50 is detected to control the bitmovement motor 50.

In the standby state of the fastening tool 1, as shown in FIG. 1A, thetip end of the driver bit 2 is positioned at the standby position P1 onthe rear side of the injection passage 80, and the screw 200 can besupplied to the injection passage 80.

In step SF1 of FIG. 25 , the control unit 100 sets the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2 based on a setting value selected by thesetting portion 110. When the contact member 81 is pressed against thefastening target, the contact switch portion 84 is pressed by thecontact arm 82, the contact switch portion 84 is turned on in step SF2,the trigger 9 is operated, and the trigger switch portion 90 is turnedon in step SF3, the control unit 100 drives the bit rotation motor 40 ofthe first drive unit 4 in step SF4, and drives the bit movement motor 50of the second drive unit 5 in step SF5.

When the bit movement motor 50 is driven to rotate in the positivedirection, which is the one direction, the pulley 52 rotates in thepositive direction, so that the wire 54 is wound around the pulley 52,and the moving member 32 in which the second moving member 32 c isconnected to the wire 54 and the holding member 30 connected to themoving member 32 by the first moving member 32 a move in the forwarddirection.

Accordingly, the driver bit 2 held by the holding member 30 moves in theforward direction indicated by the arrow A1, engages with the screw 200supplied to the injection port 81 a of the nose portion 8, moves thescrew 200 in the forward direction, and presses the screw 200 againstthe fastening target.

When the bit rotation motor 40 is driven to rotate in the positivedirection, which is the one direction, the holding member 30 rotatestogether with the rotation guide member 31.

Accordingly, the driver bit 2 held by the holding member 30 rotates thescrew 200 in the positive direction (clockwise) and screws the screw 200into the fastening target. The control unit 100 moves the driver bit 2in the forward direction by the second drive unit 5 in conjunction withan operation of rotating the driver bit 2 by the first drive unit 4 toscrew the screw into the fastening target, thereby causing the driverbit 2 to follow the screw to be screwed into the fastening target.

In step SF6, the control unit 100 determines whether the number ofrotations of the bit movement motor 50 reaches the setting valueselected by the setting portion 110 and the tip end of the driver bit 2reaches the set operation end position P2. When it is determined thatthe number of rotations of the bit movement motor 50 does not reach thesetting value selected by the setting portion 110, the control unit 100detects a load applied to the bit movement motor 50 in step SF7, andwhen the control unit 100 detects a predetermined load, the control unit100 controls the bit movement motor 50 in step SF8.

When the holding member 30 and the moving member 32 move in the forwarddirection by driving of the bit movement motor 50, in order to preventoccurrence of an excessive impact when the screw 200 is pressed againstthe fastening target, the bit rotation motor 40 performs maximum outputwithin an assumed range in order to prevent a fastening speed from beingdecreased, and output of the bit movement motor 50 is limited bylowering a voltage value applied to the bit movement motor 50, loweringa current value supplied to the bit movement motor 50, or the like.

When a ratio of a forward movement amount of the driver bit 2 perrotation of the bit movement motor 50 to a forward movement amount ofthe screw per rotation of the bit rotation motor 40 becomes low, theforward movement amount of the driver bit 2 by the bit movement motor 50cannot catch up with the forward movement amount of the screw by the bitrotation motor 40, and therefore cam-out occurs. On the other hand, whenthe ratio of the forward movement amount of the driver bit 2 perrotation of the bit movement motor 50 to the forward movement amount ofthe screw per rotation of the bit rotation motor 40 becomes high, theforward movement amount of the driver bit 2 by the bit movement motor 50greatly exceeds the forward movement amount of the screw by the bitrotation motor 40, and therefore an excessive force is required to pressthe fastening tool 1 in a fastening target direction by the operator.

Therefore, as a target value of an output limitation, it is preferablethat the ratio of the forward movement amount of the driver bit 2 perrotation of the bit movement motor 50 to the forward movement amount ofthe screw per rotation of the bit rotation motor 40 is about 0.8 time to5 times. Accordingly, it is possible to prevent occurrence of cam-out,and without requiring an excessive force for pressing the fastening tool1 toward the fastening target direction by the operator, it is possibleto prevent occurrence of an excessive impact when the screw 200 ispressed against the fastening target.

When the load on the bit movement motor 50 generated after the fasteningtarget and the screw 200 contact with each other is detected, the outputof the bit movement motor 50 is limited, and thus, when the screw 200 ispressed against the fastening target, the holding member 30 and themoving member 32 are decelerated, so that it is possible to obtain aneffect of further preventing impact.

In control for limiting output of the bit movement motor 50, as shown inFIG. 26A, after a predetermined load is detected, the output of the bitmovement motor 50 may be limited so that the rotation speed becomesconstant until the bit rotation motor 40 rotates at the number ofrotations for moving the driver bit 2 to the operation end position. Asshown in FIG. 26B, the bit movement motor 50 is rotated forward at afirst rotation speed until the predetermined load is detected. After thepredetermined load is detected, the bit movement motor 50 is rotatedforward at a second rotation speed that is reduced in the rotation speedin order to weaken impact when the screw 200 is pressed against thefastening target. Further, after a predetermined buffering time elapsesin which the impact when the screw 200 is pressed against the fasteningtarget is weakened, the output may be limited so as to be a constantrotation speed at a third rotation speed that is slower than the firstrotation speed and faster than the second rotation speed until the bitrotation motor 40 rotates at the number of rotations for moving thedriver bit 2 to the operation end position.

A fluctuation in the power supply voltage causes a difference in themoving speed (forward speed) of the holding member 30 and the movingmember 32. The higher the power supply voltage, the faster the movingspeed, and the more likely an excessive impact occurs when the screw 200is pressed against the fastening target. Therefore, the control unit 100detects the power supply voltage, and decreases the output of the bitmovement motor 50 as the power supply voltage is high, as compared withthe case where the power supply voltage is low.

Accordingly, occurrence of the difference in the rotation speed of thebit movement motor 50 due to the fluctuation in the power supply voltageis prevented. Therefore, when the screw 200 is pressed against thefastening target, occurrence of an excessive impact is prevented, andoccurrence of variation in a speed at which the screw 200 is pressedagainst the fastening target is prevented.

When it is determined that the number of rotations of the bit movementmotor 50 reaches the setting value selected by the setting portion 110and the tip end of the driver bit 2 reaches the set operation endposition P2 in step SF6, the control unit 100 stops driving of the bitrotation motor 40 in step SF9, stops rotation of the bit movement motor50 in the positive direction in step SF10, and then reversely rotatesthe bit movement motor 50 in step SF11.

When the bit movement motor 50 rotates in the reverse direction, whichis the other direction, the pulley 52 rotates in the reverse direction,so that the wire 54 is pulled out from the pulley 52, and the movingmember 32 in which the second moving member 32 c is pressed by thebiasing member 33 and the holding member 30 connected to the movingmember 32 by the first moving member 32 a move in the rearwarddirection.

When the bit movement motor 50 rotates reversely to an initial positionwhere the wire 54 is pulled out from the pulley 52 by a predeterminedamount and the holding member 30 and the moving member 32 move in therearward direction to a position where the tip end of the driver bit 2returns to the standby position P1 in step SF12, the control unit 100stops the reverse rotation of the bit movement motor 50 in step SF13.

FIG. 27 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment. Next, the othermodification of the fastening operation of the fastening tool accordingto the present embodiment will be described with reference to thedrawings. In this modification, a load applied to the bit movement motor50 or the like is detected, and driving in a state where there is noscrew is prevented.

In the standby state of the fastening tool 1, as shown in FIG. 1A, thetip end of the driver bit 2 is positioned at the standby position P1 onthe rear side of the injection passage 80, and the screw 200 can besupplied to the injection passage 80.

In step SG1 of FIG. 27 , the control unit 100 sets the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2 based on a setting value selected by thesetting portion 110. When the contact member 81 is pressed against thefastening target, the contact switch portion 84 is pressed by thecontact arm 82, the contact switch portion 84 is turned on in step SG2,the trigger 9 is operated, and the trigger switch portion 90 is turnedon in step SG3, the control unit 100 drives the bit rotation motor 40 ofthe first drive unit 4 in step SG4, and drives the bit movement motor 50of the second drive unit 5 in step SGS.

When the bit movement motor 50 is driven to rotate in the positivedirection, which is the one direction, the pulley 52 rotates in thepositive direction, so that the wire 54 is wound around the pulley 52,and the moving member 32 in which the second moving member 32 c isconnected to the wire 54 and the holding member 30 connected to themoving member 32 by the first moving member 32 a move in the forwarddirection.

Accordingly, the driver bit 2 held by the holding member 30 moves in theforward direction indicated by the arrow A1, engages with the screw 200supplied to the injection port 81 a of the nose portion 8, moves thescrew 200 in the forward direction, and presses the screw 200 againstthe fastening target.

When the bit rotation motor 40 is driven to rotate in the positivedirection, which is the one direction, the holding member 30 rotatestogether with the rotation guide member 31.

Accordingly, the driver bit 2 held by the holding member 30 rotates thescrew 200 in the positive direction (clockwise) and screws the screw 200into the fastening target. The control unit 100 moves the driver bit 2in the forward direction by the second drive unit 5 in conjunction withan operation of rotating the driver bit 2 by the first drive unit 4 toscrew the screw into the fastening target, thereby causing the driverbit 2 to follow the screw to be screwed into the fastening target.

In step SG6, the control unit 100 determines whether the number ofrotations of the bit movement motor 50 reaches the setting valueselected by the setting portion 110 and the tip end of the driver bit 2reaches the set operation end position P2. When it is determined thatthe number of rotations of the bit movement motor 50 does not reach thesetting value selected by the setting portion 110, the control unit 100detects a load applied to one or both of the bit rotation motor 40 andthe bit movement motor 50 in step SG7. When the screw 200 is pressedagainst the fastening target and a predetermined load is detected, thebit movement motor 50 continues to rotate in the positive directionuntil the number of rotations of the bit movement motor 50 reaches thesetting value selected by the setting portion 110.

When the control unit 100 determines that the number of rotations of thebit movement motor 50 reaches the setting value selected by the settingportion 110 and the tip end of the driver bit 2 reaches the setoperation end position P2 in step SG6, the control unit 100 stopsdriving of the bit rotation motor 40 in step SG8, stops rotation of thebit movement motor 50 in the positive direction in step SG9, and thenreversely rotates the bit movement motor 50 in step SG10.

When the bit movement motor 50 rotates in the reverse direction, whichis the other direction, the pulley 52 rotates in the reverse direction,so that the wire 54 is pulled out from the pulley 52, and the movingmember 32 in which the second moving member 32 c is pressed by thebiasing member 33 and the holding member 30 connected to the movingmember 32 by the first moving member 32 a move in the rearwarddirection.

When the bit movement motor 50 rotates reversely to an initial positionwhere the wire 54 is pulled out from the pulley 52 by a predeterminedamount and the holding member 30 and the moving member 32 move in therearward direction to a position where the tip end of the driver bit 2returns to the standby position P1 in step SG11, the control unit 100stops the reverse rotation of the bit movement motor 50 in step SG12.

When the bit rotation motor 40 and the bit movement motor 50 rotate inthe positive direction in a state where the screw 200 is not in theinjection port 81 a, the screw 200 is not pressed against the fasteningtarget, so that loads applied to the bit rotation motor 40 and the bitmovement motor 50 do not increase. Therefore, if a predetermined load isnot detected even if the driver bit 2 attached to the holding member 30moves forward by a specified movement amount with reference to a lengthof the smallest screw 200 to be loaded, it can be determined that thereis no screw 200.

Therefore, in step SG13, the control unit 100 determines whether the bitmovement motor 50 rotates by a specified movement amount with referenceto the length of the smallest screw 200 to be loaded or by a specifiedamount of idle rotation detection by which the driver bit 2 attached tothe holding member 30 moves forward. When it is determined that apredetermined load is not detected in one or both of the bit rotationmotor 40 and the bit movement motor 50 and that the bit movement motor50 rotates by the specified amount of idle rotation detection, thecontrol unit 100 determines that there is no screw 200, and notifies anerror in step SG14. In processing of steps SG8 to SG12 described above,driving of the bit rotation motor 40 and the bit movement motor 50 isstopped.

The control unit 100 may detect the load applied to one or both of thebit rotation motor 40 and the bit movement motor 50 by a change in acurrent flowing through the motor except for a change in the currentgenerated at the time of starting the motor. The detection may beperformed based on a change in a voltage flowing through the motorexcept for a change in the voltage generated at the time of starting themotor. The rotation of the bit holding portion 3 and the movement of thebit holding portion 3 in the axial direction may be performed by asingle motor. The control unit 100 may detect a load applied to thesingle motor and prevent driving in a state in which there is no screw.

Next, another modification of the fastening operation of the fasteningtool according to the present embodiment will be described. In thismodification, in the feedback control in which the moving speed of thedriver bit by the bit movement motor 50 follows (is synchronized with)the moving speed of the screw by the rotation of the bit rotation motor40, a moving speed of the bit holding portion 3 is calculated using alead length of the screw 200 acquired at the time of a previous screwtightening operation. In the present modification, the lead length ofthe screw 200 means a distance by which the screw 200 advances in onerotation.

FIG. 28 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment. Since a graphshowing a relationship between the rotation speeds of the bit rotationmotor and the bit movement motor under the feedback (FB) control is thesame as that in FIG. 24A, and a graph showing a relationship between themoving speed of the screw by the rotation of the bit rotation motor andthe moving speed of the driver bit by the bit movement motor under thefeedback (FB) control is the same as that in FIG. 24B, the descriptionof each graph will be described with reference to FIGS. 24A and 24B.

In the standby state of the fastening tool 1, as shown in FIG. 1A, thetip end of the driver bit 2 is positioned at the standby position P1 onthe rear side of the injection passage 80, and the screw 200 can besupplied to the injection passage 80.

In step SH1 of FIG. 28 , the control unit 100 sets the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2 based on a setting value selected by thesetting portion 110. When the contact member 81 is pressed against thefastening target, the contact switch portion 84 is pressed by thecontact arm 82, the contact switch portion 84 is turned on in step SH2,the trigger 9 is operated, and the trigger switch portion 90 is turnedon in step SH3, the control unit 100 drives the bit rotation motor 40 ofthe first drive unit 4 in step SH4, and drives the bit movement motor 50of the second drive unit 5 in step SH5.

When the bit movement motor 50 is driven to rotate in the positivedirection, which is the one direction, the pulley 52 rotates in thepositive direction, so that the wire 54 is wound around the pulley 52,and the moving member 32 in which the second moving member 32 c isconnected to the wire 54 and the holding member 30 connected to themoving member 32 by the first moving member 32 a move in the forwarddirection.

Accordingly, the driver bit 2 held by the holding member 30 moves in theforward direction indicated by the arrow A1, engages with the screw 200supplied to the injection port 81 a of the nose portion 8, moves thescrew 200 in the forward direction, and presses the screw 200 againstthe fastening target.

When the bit rotation motor 40 is driven to rotate in the positivedirection, which is the one direction, the holding member 30 rotatestogether with the rotation guide member 31.

Accordingly, the driver bit 2 held by the holding member 30 rotates thescrew 200 in the positive direction (clockwise) and screws the screw 200into the fastening target. The control unit 100 moves the driver bit 2in the forward direction by the second drive unit 5 in conjunction withan operation of rotating the driver bit 2 by the first drive unit 4 toscrew the screw into the fastening target, thereby causing the driverbit 2 to follow the screw to be screwed into the fastening target.

In step SH6, the control unit 100 determines whether the number ofrotations of the bit movement motor 50 reaches the setting valueselected by the setting portion 110 and the tip end of the driver bit 2reaches the set operation end position P2. When it is determined thatthe number of rotations of the bit movement motor 50 does not reach thesetting value selected by the setting portion 110, the control unit 100detects a load applied to at least one of the bit rotation motor 40 andthe bit movement motor 50 in step SH7, and when the control unit 100detects a predetermined load, the control unit 100 acquires a rotationspeed of the bit rotation motor 40 and a rotation speed of the bitmovement motor 50 in step SH8.

In step SH9, the control unit 100 calculates the target rotation speedand the like of the bit movement motor 50 using information of the leadlength of the screw 200 acquired at the time of the previous screwtightening operation. Specifically, the target rotation speed of the bitmovement motor 50 obtained based on the lead length of the screw 200,the rotation speed of the bit rotation motor 40, the gear ratio of thespeed reducer, and the like so that by fastening the screw 200 to thefastening target by the rotation of the bit rotation motor 40, themoving speed when the screw 200 is moved in the forward direction, themoving speed of the holding member 30 and the moving member 32 whichmove in the forward direction by the rotation of the bit movement motor50, and the moving speed of the driver bit 2 attached to the holdingmember 30 substantially coincide with one another as shown in FIG. 24B.For example, the control unit 100 calculates the target rotation speedof the bit movement motor 50 based on a following equation (1).

Target rotation speed of bit movement motor 50=(gear ratio of speedreducer of bit movement motor 50/gear ratio of speed reducer of bitrotation motor 40×circumferential length of pulley 52/lead length ofscrew 200)×rotation speed of bit rotation motor 40   (1)

In step SH10, the control unit 100 controls the bit movement motor 50 soas to achieve the calculated target rotation speed in the presentexample by the feedback control based on the rotation speed of the bitrotation motor 40, the gear ratio of the speed reducer, and the like.For example, the control is performed by increasing or decreasing PWMoutput to the bit movement motor 50 and adjusting the rotation speed.

In step SH11, the control unit 100 measures the number of rotations ofthe bit rotation motor 40 after detection of the load applied to the bitrotation motor 40 or the bit movement motor 50. In step SH12, thecontrol unit 100 measures the number of rotations of the bit movementmotor 50 after the detection of the load applied to the bit rotationmotor 40 or the bit movement motor 50. The number of rotations of thebit rotation motor 40 and the number of rotations of the bit movementmotor 50 measured in steps SH11 and SH12 are stored in a memory (notshown) and used in step SH18 of calculating the lead length of the screw200 at the time of a next screw tightening operation. Upon completion ofthe measurement in step SH12, the processing returns to step SH6.

When it is determined that the number of rotations of the bit movementmotor 50 reaches the setting value selected by the setting portion 110and the tip end of the driver bit 2 reaches the set operation endposition P2 in step SH6, the control unit 100 stops driving of the bitrotation motor 40 in step SH13, stops rotation of the bit movement motor50 in the positive direction in step SH14, and then reversely rotatesthe bit movement motor 50 in step SH15.

When the bit movement motor 50 rotates in the reverse direction, whichis the other direction, the pulley 52 rotates in the reverse direction,so that the wire 54 is pulled out from the pulley 52, and the movingmember 32 in which the second moving member 32 c is pressed by thebiasing member 33 and the holding member 30 connected to the movingmember 32 by the first moving member 32 a move in the rearwarddirection.

When the bit movement motor 50 rotates reversely to an initial positionwhere the wire 54 is pulled out from the pulley 52 by a predeterminedamount and the holding member 30 and the moving member 32 move in therearward direction to a position where the tip end of the driver bit 2returns to the standby position P1 in step SH16, the control unit 100stops the reverse rotation of the bit movement motor 50 in step SH17.

When a series of screw tightening operation is completed, the controlunit 100 calculates the lead length of the screw 200 in a followingprocedure in step SH18. The calculation of the lead length of the screw200 may be executed in parallel with reverse rotation control over thebit movement motor 50 or the like before and after the processing ofstep SH13 or step SH14, other than after the screw tightening operationbeing ended.

First, the number of rotations of the screw 200 is calculated based on afollowing equation (2).

Number of rotations of screw 200=number of rotations of bit rotationmotor 40 from start of screw tightening (after load detection) to end oftightening of screw 200 (step SH11)/gear ratio of speed reducer of bitrotation motor 40   (2)

In the above equation (2), the number of rotations of the bit rotationmotor 40 is acquired in an entire section from the load detection to theend of tightening of the screw 200, but the present disclosure is notlimited thereto, and the number of rotations of the bit rotation motor40 may be acquired in a part of sections of the entire section.

Next, a length of the screw 200 is calculated based on a followingequation (3).

Length of screw 200 (movement amount of driver bit 2 from start of screwtightening to end of tightening of screw 200)=number of rotations of bitmovement motor 50 from start of screw tightening to end of screwtightening (step SH12)/gear ratio of speed reducer of bit movement motor50×circumferential length of pulley 52   (3)

In the above equation (3), the number of rotations of the bit movementmotor 50 is acquired in an entire section from the load detection to theend of tightening of the screw 200, but the present disclosure is notlimited thereto, and the number of rotations of the bit movement motor50 may be acquired in a part of sections of the entire section.

Next, the lead length of the screw 200 is calculated based on afollowing equation (4).

Lead length of screw 200=length of screw 200 (equation (3))/number ofrotations of screw 200 (equation (2))   (4)

The control unit 100 stores the calculated lead length of the screw 200in the memory (not shown), and resets the calculated lead length as alead length to be used in calculating the rotation speed of the bitmovement motor 50 and the like after the load detection in the nextscrew tightening operation. Thus, in the present modification, the leadlength of the used screw 200 is determined (calculated) from the screwtightening operation of one cycle, and an entering speed (moving speed)of the driver bit 2 with respect to the fastening target per rotationand the rotation speed of the bit movement motor 50 at the time of thenext screw tightening operation are calculated using the determined leadlength.

According to the present modification, by estimating the lead length ofthe screw 200 used for the screw tightening operation, it is possible toaccurately calculate an entering depth and an entering speed of thescrew 200 into the fastening target by driving of the bit rotation motor40. Accordingly, it is possible to cause the moving speed of the driverbit 2 to follow the entering speed of the screw 200 with high accuracyduring the screw tightening after the load detection, and it is possibleto reduce a work load by reducing a force pressing the fastening tool 1at the time of the screw tightening, and it is possible to improvedriving quality by preventing occurrence of floating up of the fasteningtool 1.

Next, another modification of the fastening operation of the fasteningtool according to the present embodiment will be described. In thismodification, in the feedback control in which the moving speed of thedriver bit by the bit movement motor 50 follows the moving speed of thescrew by the rotation of the bit rotation motor 40, the target rotationspeed of the bit movement motor 50 is calculated using the lead lengthof the screw set by a lead length setting portion 120.

FIG. 29 is a block diagram showing another modification of the operationof the fastening tool according to the present embodiment. As shown inFIG. 29 , the bit rotation motor 40, the bit movement motor 50, thecontact switch portion 84, the trigger switch portion 90, the settingportion 110, and the lead length setting portion 120 are connected tothe control unit 100 of a fastening tool 1A.

The lead length setting portion 120 receives setting of the lead lengthaccording to a type of the screw 200, and outputs information of thereceived lead length to the control unit 100. The lead length settingportion 120 may be provided in the tool body 10, for example. In thiscase, the lead length setting portion 120 may be implemented by anoperation portion such as a button or a rotary dial. By operating thebutton or the like, the user may manually and directly input the leadlength of the screw 200, or the user may select a specific lead lengthfrom a plurality of lead lengths set in advance. For example, aninformation processing terminal such as a personal computer, a tablet,or a smartphone may be provided with a function of the lead lengthsetting portion 120. The lead length of the screw 200 input by theinformation processing terminal may be transmitted to the control unit100 in the fastening tool 1 by wired or wireless communication.

The control unit 100 changes the lead length used when calculating therotation speed of the bit movement motor 50 to be described later to thelead length of the screw 200 set by the lead length setting portion 120.Accordingly, information of the lead length of the screw 200 at the timeof the previous screw tightening operation can be switched toinformation of the lead length that matches the type of the screw 200used in a current screw tightening operation.

FIG. 30 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment. Since a graphshowing a relationship between the rotation speeds of the bit rotationmotor and the bit movement motor under the feedback (FB) control is thesame as that in FIG. 24A, and a graph showing a relationship between themoving speed of the screw by the rotation of the bit rotation motor andthe moving speed of the driver bit by the bit movement motor under thefeedback (FB) control is the same as that in FIG. 24B, the descriptionof each graph will be described with reference to FIGS. 24A and 24B.

In the standby state of the fastening tool 1A, as shown in FIG. 1A, thetip end of the driver bit 2 is positioned at the standby position P1 onthe rear side of the injection passage 80, and the screw 200 can besupplied to the injection passage 80.

In step SI1 of FIG. 30 , the control unit 100 sets the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2 based on a setting value selected by thesetting portion 110.

In step SI2, the lead length setting portion 120 receives setting of thelead length according to the type of the screw 200 based on an operationof the operator. When the setting of the lead length is received, theprocessing proceeds to step S13. When the setting of the lead length ofthe screw 200 is not received, the setting of the lead length used inthe previous screw tightening operation is maintained.

In step SI3, the control unit 100 sets the lead length of the screw 200received by the lead length setting portion 120 as the lead length usedwhen calculating the rotation speed of the bit movement motor 50 to bedescribed later. Information on the lead length of the screw 200received by the lead length setting portion 120 is stored in the memory(not shown). When a new lead length is set, the processing proceeds tostep SI4.

When the contact member 81 is pressed against the fastening target, thecontact switch portion 84 is pressed by the contact arm 82, the contactswitch portion 84 is turned on in step SI4, the trigger 9 is operated,and the trigger switch portion 90 is turned on in step SI5, the controlunit 100 drives the bit rotation motor 40 of the first drive unit 4 instep SI6, and drives the bit movement motor 50 of the second drive unit5 in step SI7.

When the bit movement motor 50 is driven to rotate in the positivedirection, which is the one direction, the pulley 52 rotates in thepositive direction, so that the wire 54 is wound around the pulley 52,and the moving member 32 in which the second moving member 32 c isconnected to the wire 54 and the holding member 30 connected to themoving member 32 by the first moving member 32 a move in the forwarddirection. Accordingly, the driver bit 2 held by the holding member 30moves in the forward direction indicated by the arrow A1, engages withthe screw 200 supplied to the injection port 81 a of the nose portion 8,moves the screw 200 in the forward direction, and presses the screw 200against the fastening target.

When the bit rotation motor 40 is driven to rotate in the positivedirection, which is the one direction, the holding member 30 rotatestogether with the rotation guide member 31. Accordingly, the driver bit2 held by the holding member 30 rotates the screw 200 in the positivedirection (clockwise) and screws the screw 200 into the fasteningtarget. The control unit 100 moves the driver bit 2 in the forwarddirection by the second drive unit 5 in conjunction with an operation ofrotating the driver bit 2 by the first drive unit 4 to screw the screwinto the fastening target, thereby causing the driver bit 2 to followthe screw to be screwed into the fastening target.

In step SI8, the control unit 100 determines whether the number ofrotations of the bit movement motor 50 reaches the setting valueselected by the setting portion 110 and the tip end of the driver bit 2reaches the set operation end position P2. When it is determined thatthe number of rotations of the bit movement motor 50 does not reach thesetting value selected by the setting portion 110, the control unit 100proceeds to step SI9.

The control unit 100 detects whether a load is applied to at least oneof the bit rotation motor 40 and the bit movement motor 50 in step SI9,and when the control unit 100 detects a predetermined load, the controlunit 100 acquires a rotation speed of the bit rotation motor 40 and arotation speed of the bit movement motor 50 in step SI10.

In step SI11, the control unit 100 obtains target rotation speeds of thebit rotation motor 40 and the bit movement motor 50 based on the leadlength of the screw 200 set by the lead length setting portion 120, therotation speed of the bit rotation motor 40, the rotation speed of thebit movement motor 50, the gear ratio of the speed reducer, and the likeso that by fastening the screw 200 to the fastening target by therotation of the bit rotation motor 40, the moving speed when the screw200 is moved in the forward direction and the moving speed of the driverbit 2 which moves in the forward direction by the rotation of the bitmovement motor 50 substantially coincide with each other (see FIG. 24B).For example, the control unit 100 calculates the target rotation speedof the bit movement motor 50 based on a following equation (5).

Target rotation speed of bit movement motor 50=(gear ratio of speedreducer of bit movement motor 50/gear ratio of speed reducer of bitrotation motor 40×circumferential length of pulley 52/lead length ofscrew 200)×rotation speed of bit rotation motor 40   (5)

In step SI12, the control unit 100 controls the bit movement motor 50 soas to achieve the calculated target rotation speed in the presentexample by the feedback control based on the rotation speed of the bitrotation motor 40, the rotation speed of the bit movement motor 50, thegear ratio of the speed reducer, and the like. For example, the controlis performed by increasing or decreasing PWM output to the bit movementmotor 50 and adjusting the rotation speed.

When it is determined that the number of rotations of the bit movementmotor 50 reaches the setting value selected by the setting portion 110and the tip end of the driver bit 2 reaches the set operation endposition P2 in step SI8, the control unit 100 stops driving of the bitrotation motor 40 in step SI13, stops rotation of the bit movement motor50 in the positive direction in step SI14, and then reversely rotatesthe bit movement motor 50 in step SI15.

When the bit movement motor 50 rotates in the reverse direction, whichis the other direction, the pulley 52 rotates in the reverse direction,so that the wire 54 is pulled out from the pulley 52, and the movingmember 32 in which the second moving member 32 c is pressed by thebiasing member 33 and the holding member 30 connected to the movingmember 32 by the first moving member 32 a move in the rearwarddirection.

When the bit movement motor 50 rotates reversely to an initial positionwhere the wire 54 is pulled out from the pulley 52 by a predeterminedamount and the holding member 30 and the moving member 32 move in therearward direction to a position where the tip end of the driver bit 2returns to the standby position P1 in step SI16, the control unit 100stops the reverse rotation of the bit movement motor 50 in step SI17.

A unit that switches the setting of the lead length of the screw 200 maybe other than the lead length setting portion 120. Specifically, acommunication unit may be provided in the fastening tool 1A or the like,a non-power supply communication unit may be provided on a connectingband (reel) side to which a plurality of screws 200 loaded in the screwaccommodating portion 6 are attached, and short-range wirelesscommunication may be performed between the communication unit and thenon-power supply communication unit. A non-wireless communication unitstores, for example, an IC chip in which the type of the screw 200 andthe lead length of the screw 200 are stored in association with eachother. When the connecting band is accommodated in the screwaccommodating portion 6, the communication unit wirelessly communicateswith the non-wireless communication unit to acquire the lead length ofthe screw 200 for performing the screw tightening operation, and thecontrol unit 100 switches the setting of the lead length to the acquirednew lead length. Examples of a short-range wireless communication methodinclude a non-contact method using an electromagnetic field, a radiowave, or the like, Bluetooth (registered trademark), and the like.

A unit that switches the setting of the lead length of the screw 200 maybe an identification unit that mechanically identifying a dimension ofthe connecting band loaded in the screw accommodating portion 6. In thiscase, the lead length varies depending on the type of the screw 200, andalong with this, a width of the connecting band, a position of a groove,the number, and the like are also different. Therefore, the lead lengthof the screw 200 is acquired by mechanically identifying a type of theconnecting band from a difference of these connecting bands.

According to the present modification, even when the type of the screw200 to be used is different, the lead length setting portion 120 canswitch the setting of the lead length. Therefore, since the lead lengthcan be switched to the lead length of the screw 200 actually used in thescrew tightening operation, for example, compared with a case where therotation speed of the bit movement motor 50 is calculated using aprevious lead length, it is possible to accurately calculate theentering depth and the entering speed of the screw 200 into thefastening target by driving of the bit rotation motor 40. Accordingly,it is possible to cause the moving speed of the driver bit 2 to followthe entering speed of the screw 200 with high accuracy during the screwtightening after the load detection, and it is possible to reduce a workload by reducing a force pressing the fastening tool 1A at the time ofthe screw tightening, and it is possible to improve driving quality bypreventing occurrence of floating up of the fastening tool 1A.

Next, another modification of the fastening operation of the fasteningtool according to the present embodiment will be described. In thismodification, in the feedback control in which the moving speed of thedriver bit by the bit movement motor 50 follows (is synchronized with)the moving speed of the screw by the rotation of the bit rotation motor40, a current value of the bit movement motor 50 is controlled to fallwithin a range of specified values during the screw tighteningoperation.

FIG. 31 is a flowchart showing another modification of the operation ofthe fastening tool according to the present embodiment. FIG. 32 is agraph showing a relationship between a load and control over the bitmovement motor. FIG. 33 is a view showing an engagement state betweenthe driver bit and a recess of the screw at the time of the screwtightening.

In the standby state of the fastening tool 1, as shown in FIG. 1A, thetip end of the driver bit 2 is positioned at the standby position P1 onthe rear side of the injection passage 80, and the screw 200 can besupplied to the injection passage 80.

In step SJ1 of FIG. 31 , the control unit 100 sets the number ofrotations of the bit movement motor 50 that defines the forward movementamount of the driver bit 2 based on a setting value selected by thesetting portion 110. When the contact member 81 is pressed against thefastening target, the contact switch portion 84 is pressed by thecontact arm 82, the contact switch portion 84 is turned on in step SJ2,the trigger 9 is operated, and the trigger switch portion 90 is turnedon in step SJ3, the control unit 100 drives the bit rotation motor 40 ofthe first drive unit 4 in step SJ4, and drives the bit movement motor 50of the second drive unit 5 in step SJ5.

When the bit movement motor 50 is driven to rotate in the positivedirection, which is the one direction, the pulley 52 rotates in thepositive direction, so that the wire 54 is wound around the pulley 52,and the moving member 32 in which the second moving member 32 c isconnected to the wire 54 and the holding member 30 connected to themoving member 32 by the first moving member 32 a move in the forwarddirection.

Accordingly, the driver bit 2 held by the holding member 30 moves in theforward direction indicated by the arrow A1, engages with the screw 200supplied to the injection port 81 a of the nose portion 8, moves thescrew 200 in the forward direction, and presses the screw 200 againstthe fastening target.

When the bit rotation motor 40 is driven to rotate in the positivedirection, which is the one direction, the holding member 30 rotatestogether with the rotation guide member 31.

Accordingly, the driver bit 2 held by the holding member 30 rotates thescrew 200 in the positive direction (clockwise) and screws the screw 200into the fastening target. The control unit 100 moves the driver bit 2in the forward direction by the second drive unit 5 in conjunction withan operation of rotating the driver bit 2 by the first drive unit 4 toscrew the screw into the fastening target, thereby causing the driverbit 2 to follow the screw to be screwed into the fastening target.

In step SJ6, the control unit 100 determines whether the number ofrotations of the bit movement motor 50 reaches the setting valueselected by the setting portion 110 and the tip end of the driver bit 2reaches the set operation end position P2. When it is determined thatthe number of rotations of the bit movement motor 50 does not reach thesetting value selected by the setting portion 110, the control unit 100detects a load applied to the bit movement motor 50 in step SJ7, andwhen the control unit 100 detects a predetermined load, the control unit100 acquires the number of rotations of the bit movement motor 50 instep SJ8.

When the control unit 100 determines in step SJ9 that the screwtightening operation is being performed based on the detection of thepredetermined load, the control unit 100 sets the current value of thebit movement motor 50 in accordance with the acquired number ofrotations of the bit movement motor 50 so that the current value of thebit movement motor 50 falls within a range of specified values set inadvance. Accordingly, at the time of the screw tightening operation, forexample, even in a case where forward movement of the screw 200 is fastor slow depending on a state of the fastening target, an output torqueis constant. Therefore, after causing the driver bit 2 to follow thescrew 200 moving forward, it is possible to perform the screw tighteningoperation without requiring an excessive force for the operator to pressthe fastening tool 1 against the fastening target.

As shown in FIG. 32 , after the load of the screw tightening isdetected, a target value of the current of the bit movement motor 50 isset so as to gradually increase in accordance with an increase in theload during the screw tightening operation or a decrease in the rotationspeed of the bit rotation motor 40 during the screw tighteningoperation. This is because of a following reason. Although it isnecessary to maintain engagement between the driver bit 2 and the recessof the screw during the screw tightening operation, when the screwtightening operation proceeds and the load during the screw tighteningoperation increases, as shown in FIG. 33 , forces acting in a directionB1 and a direction B2 in which the engagement between the driver bit 2and the screw 200 is released increase along a wall surface 200 a of anengagement portion of the recess of the screw. Therefore, it isnecessary to increase a force for pressing the driver bit 2 against thescrew 200 to prevent the driver bit 2 from disengaging the screw 200,and it is desirable to increase the current value of the bit movementmotor 50 every time the screw tightening operation proceeds.

Therefore, as shown in FIG. 32 , when the current value immediatelyafter the load in the screw tightening operation is detected is set to afirst specified value T1 and the current value at an end of the screwtightening operation is set to a second specified value T2, the controlunit 100 sets the first specified value T1 to fall within a range of 10Aor more and 30A or less and sets the second specified value T2 to fallwithin a range of more than 30A and 60A or less, for example. In thiscase, the control unit 100 sets the current value of the bit movementmotor 50 so as to gradually increase from the set first specified valueT1 toward the second specified value T2 in a current control executionperiod. When the number of rotations of the bit movement motor 50acquired in step SJ8 is lower than a threshold value set in advance, itis preferable to set current values of the first specified value T1 andthe second specified value T2 to be higher values within the set ranges,compared with a case where the number of rotations of the bit movementmotor 50 is higher than the threshold value. Each of the first specifiedvalue T1 and the second specified value T2 may be appropriately changedby the operator through the operation portion or the like. After thespecified values are set, the processing proceeds to step SJ10.

In step SJ10, the control unit 100 controls the current value of the bitmovement motor 50 so that the current value falls within a range betweenthe set first specified value T1 and second specified value T2. Forexample, the control unit 100 controls the current value of the bitmovement motor 50 within a range between the first specified value T1and the second specified value T2 by PWM control by switching ON or OFFof a switching element of a drive circuit, and adjusts the rotationspeed of the bit movement motor 50.

When it is determined that the number of rotations of the bit movementmotor 50 reaches the setting value selected by the setting portion 110and the tip end of the driver bit 2 reaches the set operation endposition P2 in step SJ6, the control unit 100 stops driving of the bitrotation motor 40 in step SJ11, stops rotation of the bit movement motor50 in the positive direction in step SJ12, and then reversely rotatesthe bit movement motor 50 in step SJ13.

When the bit movement motor 50 rotates in the reverse direction, whichis the other direction, the pulley 52 rotates in the reverse direction,so that the wire 54 is pulled out from the pulley 52, and the movingmember 32 in which the second moving member 32 c is pressed by thebiasing member 33 and the holding member 30 connected to the movingmember 32 by the first moving member 32 a move in the rearwarddirection.

When the bit movement motor 50 rotates reversely to an initial positionwhere the wire 54 is pulled out from the pulley 52 by a predeterminedamount and the holding member 30 and the moving member 32 move in therearward direction to a position where the tip end of the driver bit 2returns to the standby position P1 in step SJ14, the control unit 100stops the reverse rotation of the bit movement motor 50 in step SJ15.

According to the present modification, since the current value of thebit movement motor 50 is controlled so as to fall within the rangebetween the first specified value T1 and the second specified value T2,the force (load) of pressing the screw 200 by the driver bit 2 can becontrolled to be constant. Accordingly, even in a case where the forwardmovement of the screw 200 is fast or slow depending on a working state,it is possible to cause the moving speed of the driver bit 2 to followthe entering speed of the screw 200 in a state where the engagementbetween the driver bit 2 and the recess of the screw 200 is maintained.As a result, it is possible to prevent occurrence of floating up of thefastening tool 1 and improve driving quality while reducing the workload without excessively pressing the fastening tool 1 at the time ofscrew tightening.

Furthermore, the present disclosure further relates to a fastening toolincluding: a bit holding portion which detachably holds a driver bit andis configured to rotate in a circumferential direction of the driver bitand move in an axial direction of the driver bit; a first motorconfigured to rotate the bit holding portion; a second motor configuredto move the bit holding portion along the axial direction; and a controlunit configured to control a position of the bit holding portion alongthe axial direction by the number of rotations of the second motor. Thecontrol unit performs control to cause a moving speed of the bit holdingportion moved by rotation of the second motor to follow a moving speedof a screw when the screw is moved when the screw is fastened to afastening target by rotation of the first motor.

In the present disclosure, a moving speed of the driver bit follows themoving speed of the screw when the screw is fastened to the fasteningtarget.

Furthermore, the present disclosure further relates to a fastening toolincluding: a bit holding portion which detachably holds a driver bit andis configured to rotate in a circumferential direction of the driver bitand move in an axial direction of the driver bit; a first motorconfigured to rotate the bit holding portion; a second motor configuredto move the bit holding portion along the axial direction; and a controlunit configured to control a position of the bit holding portion alongthe axial direction by the number of rotations of the second motor. Thecontrol unit controls a moving speed of the bit holding portion byrotation of the second motor with respect to a rotation speed of thefirst motor.

In the present disclosure, a moving speed of the driver bit iscontrolled in each of an operation of pressing the screw against thefastening target and an operation of fastening the screw to thefastening target.

1. A fastening tool comprising: a bit holding portion which detachablyholds a driver bit and is configured to rotate in a circumferentialdirection of the driver bit and move in an axial direction of the driverbit; a first motor configured to rotate the bit holding portion; asecond motor configured to move the bit holding portion along the axialdirection; and a control unit configured to control a position of thebit holding portion along the axial direction by the number of rotationsof the second motor, wherein the control unit is configured to control amoving speed of a screw moved by rotation of the first motor or arotation speed of the first motor.
 2. The fastening tool according toclaim 1, wherein the control unit performs is configured to control amoving speed of the bit holding portion moved by rotation of the secondmotor to follow a moving speed of a screw moved by being fastened to afastening target by rotation of the first motor.
 3. The fastening toolaccording to claim 2, wherein the control unit is configured to controla rotation speed of the second motor based on a rotation speed of thefirst motor, or control the rotation speed of the first motor based onthe rotation speed of the second motor.
 4. The fastening tool accordingto claim 2, wherein the control unit controls the moving speed of thebit holding portion moved by rotation of the second motor to follow themoving speed of the screw moved by rotation of the first motor, when aload applied to the first motor or the second motor is detected.
 5. Thefastening tool according to claim 2, wherein the control unit isconfigured to calculate a moving speed of the bit holding portion basedon a lead length of the screw.
 6. The fastening tool according to claim5, wherein the control unit is configured to calculate the lead lengthof the screw using the number of rotations of the first motor or amovement amount of the bit holding portion measured after a load appliedto the first motor or the second motor is detected, and calculate themoving speed of the bit holding portion based on the calculated leadlength.
 7. The fastening tool according to claim 5, further comprising:a lead length setting portion configured to set the lead length, whereinthe control unit is configured to calculate the moving speed of the bitholding portion based on the lead length of the screw set by the leadlength setting portion.
 8. The fastening tool according to claim 1,wherein the control unit is configured to controls a moving speed of thebit holding portion moved by rotation of the second motor based on therotation speed of the first motor.
 9. The fastening tool according toclaim 8, wherein the control unit is configured to control the movingspeed of the bit holding portion moved by rotation of the second motorbased on a load applied to the first motor or the second motor.
 10. Thefastening tool according to claim 8, wherein the control unit isconfigured to control the moving speed of the bit holding portion movedby rotation of the second motor based on a fluctuation in a power supplyvoltage.
 11. The fastening tool according to claim 9, wherein thecontrol unit controls such that the load on the second motor fallswithin a range of specified values, after the load is detected.